U.S. Department of the Interior 

U.S. Geological Survey 

Trends and Status of Flow, 

Nutrients, and Sediments 

for Selected Nontidal Sites in the 

Chesapeake Bay Watershed, 1985-98 

By Michael J. Langland, U.S. Geological Survey,
 

Joel D. Blomquist, U.S. Geological Survey,
 

and Lori A. Sprague, U.S. Geological Survey,
 

and Robert E. Edwards, Susquehanna River Basin Commission
 

Open-File Report 99-451 

Lemoyne, Pennsylvania 

2000 
U.S. DEPARTMENT OF THE INTERIOR
 

BRUCE BABBITT, Secretary
 

U.S. GEOLOGICAL SURVEY
 

Charles G. Groat, Director
 

For additional information Copies of this report may be 

write to: purchased from: 

District Chief U.S. Geological Survey 

U.S. Geological Survey Branch of Information Services 

840 Market Street Box 25286, Federal Center 

Lemoyne, Pennsylvania 17043-1586 Denver, Colorado 80225-0286 

ii 
CONTENTS
 

Page 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
 

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
 

Study methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites
 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring
 

Program sites and 21 Multi-Agency Nontidal Program sites in the Chesapeake Bay
 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring
 

Program sites and 21 Multi-Agency Nontidal Program sites in the Chesapeake Bay
 

Data set construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
 

Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
 

ESTIMATOR model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
 

Linear regression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
 

Seasonal Kendall test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
 

Kendall-Theil trend analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
 

Detection and trend reporting of censored data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
 

Trends in flow and water-quality conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
 

Monthly-mean streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
 

Monthly load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
 

Flow-weighted concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
 

Flow-adjusted concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
 

Status of flow and water-quality conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
 

Mean yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
 

Median concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
 

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
 

and 21 Multi-Agency Nontidal Program sites in the Chesapeake Bay Watershed. . . . . . . . . . . . . . . . . . 18
 

Watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
 

Watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
 

iii 
ILLUSTRATIONS
 

Page 

Figures 1-3. Maps showing: 

1. Location and site number for the 30 sites used in this study. . . . . . . . . . . . . . . . . . 2
 

2. Trends in steamflow, 1985-98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
 

3. Trends in load for total nitrogen and total phosphorus . . . . . . . . . . . . . . . . . . . . . 10
 

4-5. Graphs showing:
 

4. 	Combined annual flow and loads from the three largest rivers
 

(Susquehanna, Potomac, and James) draining into the Chesapeake
 

Bay Watershed for 1988-98 compared to long-term average flow
 

(1950-98) and the average load (1988-98) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
 

5. Comparison between observed monthly concentration and a
 

flow-weighted monthly concentration of total nitrogen. . . . . . . . . . . . . . . . . 12
 

6-7. Maps showing: 

6. Trends in flow-weighted concentrations for total nitrogen and
 

total phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
 

7. 	Trends in flow-adjusted concentrations for total nitrogen and
 

total phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
 

8. Boxplots showing percentage difference in statistically significant trends between
 

the ESTIMATOR model and the Kendall-Theil test by use of absolute values . . . . . 16
 

TABLES 

Table 1. Streamflow and water-quality station numbers for the 9 River Input Program
 

and 21 Multi-Agency Nontidal Program sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
 

2. List of constituents in U.S. Geological Survey Chesapeake Bay nontidal water-


quality database. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
 

iv 
Trends and Status of Flow, Nutrients, and Sediments
 

for Selected Nontidal Sites in the Chesapeake Bay
 

Watershed, 1985-98
 

by Michael J. Langland,
 

U.S. Geological Survey,
 

Joel D. Blomquist, U.S. Geological Survey,
 

Lori A. Sprague, U.S. Geological Survey,
 

and Robert E. Edwards, Susquehanna River 

Basin Commission 

ABSTRACT 

Data from 30 stream sites in nontidal portions 

of the Chesapeake Bay Watershed were analyzed 

to document annual nutrient and sediment loads 

and trends for the period 1985 through 1998 as part 

of an annual water-quality update for the Chesapeake Bay Program. Annual loads were estimated 

by use of the U.S. Geological Survey ESTIMATOR 

model and are available upon request. Trends were 

estimated by use of either linear regression, Seasonal Kendall, or Kendall-Theil tests. Trends were 

reported for monthly-mean flow, monthly load, 

flow-adjusted concentration, and flow-weighted 

concentration. Mean yields and median concentrations were calculated to help assess current waterquality status and to facilitate comparisons 

between basins. The trend in flow was upward at 

12 of the 30 sites. Trends of nutrient and sediment 

load were upward at these same 12 sites. Trends in 

flow–adjusted and flow-weighted concentrations 

varied by species. Trends in flow-weighted concentrations were generally upward or not significant 

for the nitrogen species and parallel or not significant for phosphorus species. Trends in flowadjusted concentrations were downward at nearly 

all sites for sediment and dissolved solids in the 

Susquehanna and Potomac River Basins and generally were not significant in the Virginia river 

basins. 

INTRODUCTION 

The ecosystem of the Chesapeake Bay has been 

adversely affected by nutrient enrichment. The 

Chesapeake Bay Program (CBP), a multi-jurisdictional restoration effort, established a goal to 

reduce controllable nutrient loads into the estuary 

by 40 percent by the year 2000. Results from the 

CBP watershed and water-quality models indicated that water quality would be sufficiently 

improved to support living resources if the 40-percent nutrient-reduction goal was met. Individual 

nutrient-reduction goals and associated strategies 

were established for the major rivers delivering 

nutrients to the Bay. Progress toward these reduction goals have been reevaluated by use of the 

watershed and water-quality models. Additionally, 

water-quality and living-resource data are compiled and analyzed to assess the response of the 

watershed to nutrient-reduction efforts. The 1998 

data-analysis effort is part of an annual effort to 

document changes in water quality and living 

resources in response to Nutrient Reduction Strategies (NRS) in the Chesapeake Bay Watershed. 

Two programs, the River Input Monitoring 

and Multi-Agency Nontidal Programs, provide 

information about water-quality conditions in the 

nontidal areas of the Bay. As part of the River Input 

Monitoring Program, water-quality and streamflow data are collected at nine stations near the Fall 

Line (fig. 1). Through the Multi-Agency Nontidal 

Program, water-quality and streamflow data are 

collected by several agencies at 21 sites upstream 

from the River Input Program sites in the nontidal 

watershed (fig. 1). The water-quality and streamflow data are used to determine trends in streamflow and in concentration and load of nutrients. At 

15 of the 21 sites, trend calculations were completed by the U.S. Geological Survey (USGS) in 

cooperation with Maryland Department of Natural 

Resources (MdDNR), Virginia Department of Environmental Quality (VaDEQ), and Washington, 

D.C., Council of Governments (WashCOG); and at 

6 sites by the Susquehanna River Basin Commission (SRBC) as part of the Susquehanna Nutrient 

Assessment Program. 

1 
Figure 1. Location and site number for the 30 sites used in this study. 

2
 
PURPOSE 

This report documents the methods used to 

estimate trends and status in flow and nutrient and 

sediment concentrations and loads and presents 

trends in flow and nutrient and sediment waterquality data from 1985 to 1998 from nontidal sites 

in the Chesapeake Bay Watershed. Water-quality 

and biological data from the tidal portions of the 

Bay will be used to assess changes in water quality 

in response to natural conditions and implementation of nutrient-reduction strategies. 

STUDY METHODS 

The methods section discusses how the data 

sets were constructed and describes the statistical 

tests used to interpret trends. Water-quality constituent loads were estimated by use of a multiparameter regression model. Trends were estimated by use of both parametric and nonparametric tests. 

Data Set Construction 

The following section describes the sources of 

the water-quality and flow data, selection of constituents, record length, and estimation of missing 

constituents used in calculations of annual loads 

and trends. 

Water-quality concentration and streamflow 

data were retrieved and compiled from the following agencies: the USGS, the U.S. Environmental 

Protection Agency (USEPA), the Pennsylvania 

Department of Environmental Protection (PaDEP), 

the MdDNR, the VaDEQ, the SRBC, the Interstate 

Commission on the Potomac River Basin (ICPRB), 

and the WashCOG. This effort was undertaken to 

update the nontidal water-quality database to 

include 1997 and 1998 data at the 30 sites. This 

database originally consisted of data from 1972 

through 1992 (Langland and others, 1995) and was 

updated through 1996 (Langland and others, 1998). 

The 30 sites analyzed as part of the 1998 Chesapeake Bay Program water-quality update are listed 

in table 1. 

Data for a total of 38 physical, biological, and 

chemical water-quality constituents (table 2) were 

retrieved, if available, and updated for the 30 sites 

in table 1. These constituents include 14 nutrient 

species, suspended sediment, and total suspended 

solids. Continuous daily streamflow data were 

retrieved from the USGS National Water Information System (NWIS) database. The updated waterquality database and the USGS streamflow database provided the input data files to estimate 

annual loads and trends. Constituent concentration data were quality assured by use of a statistical program that identified suspect remark codes 

(such as less than detection or greater-than values), 

missing dates and/or missing times associated 

with the sample before they were added to the 

database. Additionally, the raw and residual data 

were visually examined before their use in the various trend and load analysis programs. 

The following nitrogen, phosphorus, and sediment/solids species were tested for trend and have 

estimated annual loads where applicable. Because 

of analytical differences between SED and TSS 

determinations, SED concentrations tend to be 

higher and more variable than TSS concentrations 

(Kammerer and others, 1998). Therefore, caution 

should be used when comparing the two. 

Nitrogen species: 

Total nitrogen TN 

Dissolved Kjeldahl nitrogen DKN 

Total Kjeldahl nitrogen TKN 

Total ammonia TNH3 

Dissolved ammonia DNH3 

Total or dissolved nitrate, or total or NOx 

dissolved nitrite plus nitrate 

Phosphorus species: 

Total phosphorus TP 

Dissolved phosphorus DP 

Dissolved inorganic phosphorus DIP 

Suspended sediment SED 

Total suspended solids TSS 

In some data sets, water-quality records were 

missing for some constituents. Where possible, the 

concentration of missing constituents was calculated from the reported species of the constituent. 

For example, if the concentration of total nitrogen 

was missing, an estimated value was obtained by 

adding total Kjeldahl (total organic nitrogen plus 

total ammonia) and total nitrite plus nitrate. If total 

nitrite plus nitrate was missing, the sum of the 

total nitrite and total nitrate was used if available. 

If more than one of the nitrogen species used in 

calculating total nitrogen was below the detection 

limit, the estimated value was not determined or 

reported as less than the combined minimum 

reporting limit. In some data sets, total nitrogen 

and total phosphorus are calculated as the sum of 

the particulate and dissolved constituents. The 

concentration of missing constituents was estimated ONLY for input data files used to calculate 

loads and trends. Missing values in the statistical 

database were not populated. 

3 
Table 1. Streamflow and water-quality station numbers for the 9 River Input Program and 21 Multi-Agency Nontidal 

Program sites 

Streamflow 

station 

Water-quality 

station Latitude Longitude Map ID 

Drainage area 

(square miles) Station name 

River Input Program Sites 

01491000 01491000 385950 754710 9 113 Choptank River near Greensboro, Md. 

01578310 01578310 393928 761029 8 27,100 Susquehanna River at Conowingo, Md. 

01594440 01594440 385721 764136 11 348 Patuxent River near Bowie, Md. 

01646580 PR01 385546 770701 22 11,600 Potomac River at Chain Bridge, Md. 

01668000 01668000 381920 773105 24 1,596 Rappahannock River near Fredericksburg, Va. 

01673000 01673000 374603 771957 25 1,081 Pamunkey River near Hanover, Va. 

01674500 01674500 375316 770948 27 601 Mattaponi River near Beulahville, Va. 

02035000 02035000 374015 780510 29 6,257 James River at Cartersville, Va. 

02041650 02041650 371330 772832 30 1,344 Appomattox River at Matoaca, Va. 

Multi-Agency Nontidal Program Sites 

01531500 01531500 414555 762628 1 7,797 Susquehanna River at Towanda, Pa. 

01540500 01540500 405729 763710 2 11,220 Susquehanna River at Danville, Pa. 

01553500 01553500 405803 765236 3 6,859 West Branch Susquehanna River at Lewisburg, Pa. 

01567000 01567000 402842 770746 4 3,354 Juniata River at Newport, Pa. 

01570000 01570000 401508 770117 5 470 Conodoguinet Creek near Hogestown, Pa. 

01576000 01576000 400316 763152 6 25,990 Susquehanna River at Marietta, Pa. 

01576754 01576754 395647 762205 7 470 Conestoga River at Conestoga, Pa. 

01586000 NPA0165 393000 765300 12 56.6 North Branch Patapsco River at Cederhurst, Md. 

01592500 PXT0809 390700 765231 10 132 Patuxent River at Laurel, Md. 

01599000 GEO0009 392936 790242 13 47 Georges Creek near Franklin, Md. 

01601500 WIL0013 393941 784650 14 247 Wills Creek near Cumberland, Md. 

01610000 POT2766 393218 782717 15 3,109 Potomac River at Paw Paw, W. Va. 

01613000 POT2386 394149 781036 16 4,073 Potomac River at Hancock, Md. 

01614500 CON0180 394256 774931 17 501 Conococheague Creek at Fairview, Md. 

01643000 MON0155 392313 772158 18 817 Monocacy River at Reels Mill Road, Md. 

01638500 POT1595 391624 773238 19 9,651 Potomac River at Point of Rocks, Md. 

01631000 1BSSF003.56 385449 781240 20 1,642 South Fork Shenandoah River at Front Royal, Va. 

01634000 1BNFS010.34 385836 782011 21 768 North Fork Shenandoah River near Strasburg, Va. 

01666500 3-ROB001.90 381930 780545 23 179 Robinson River near Locust Dale, Va. 

01671020 8-NAR005.42 375100 772541 26 463 North Anna River at Hart Corner near Doswell, Va. 

02013100 2-JKS023.61 374719 800003 28 614 Jackson River below Dunlap Creek at Covington, Va. 

4 
Table 2. List of constituents in U.S. Geological Survey Chesapeake Bay nontidal water-quality database 

[ft3/s, cubic feet per second; mg/L, milligrams per liter; μg/L, micrograms per liter; N, nitrogen; P, phosphorus; 

C, carbon; CaCO3, calcium carbonate; g/m2, grams per square meter] 

Constituent 

code Data description Constituentcode Data description 

STAID 

SNAME 

AGENCY 

DATE 

TIME 

LAT 

LONG 

HUC 

00010 

00060 

00061 

00065 

00076 

00095 

00300 

00400 

00410 

00530 

00600 

00608 

00610 

00613 

00615 

Station number 

Station name 

Collection agency code 

Date of sample collection 

Time of sample collection 

Latitude 

Longitude 

Hydrologic unit code 

Water temperature, in degrees Celsius 

Daily mean discharge, in ft3/s 

Instantaneous discharge, in ft3/s 

Stream stage, in feet 

Turbidity, in NTU 

Specific conductance, in microsiemens per centimeter 

Dissolved oxygen, in mg/L 

pH, in pH units 

Total alkalinity as CaCO3, in mg/L 

Total suspended solids at 105 degrees Celsius, in mg/L 

Total nitrogen as N, in mg/L 

Dissolved ammonia as N, in mg/L 

Total ammonia as N, in mg/L 

Dissolved nitrite as N, in mg/L 

Total nitrite as N, in mg/L 

00618 

00620 

00623 

00625 

00630 

00631 

00665 

00671 

00680 

00681 

00900 

00915 

00925 

00930 

00935 

00940 

00945 

00955 

32211 

32231 

32232 

49954 

80154 

Dissolved nitrate as N, in mg/L 

Total nitrate as N, in mg/L 

Dissolved ammonia plus organic nitrogen as N, in mg/L 

Total ammonia plus organic nitrogen as N, in mg/L 

Total nitrate plus nitrite as N, in mg/L 

Dissolved nitrate plus nitrite as N, in mg/L 

Total phosphorus as P, in mg/L 

Dissolved inorganic phosphorus as P, in mg/L 

Total organic carbon as C, in mg/L 

Dissolved organic carbon as C, in mg/L 

Hardness as CaCO3, in mg/L 

Dissolved calcium as Ca, in mg/L 

Dissolved magnesium as Mg, in mg/L 

Dissolved sodium as Na, in mg/L 

Dissolved potassium as K, in mg/L 

Dissolved chlorine as Cl, in mg/L 

Dissolved sulfate as SO4, in mg/L 

Dissolved silica as SiO2, in mg/L 

Chlorophyll a, in μg/L 

Chlorophyll b, in μg/L 

Chlorophyll c, in μg/L 

Periphyton algal dry mass, in g/m2 

Total suspended sediment, in mg/L 

5 
For trend results to be most useful for the 

1998 water-quality update, the time series would 

ideally begin in January 1985 and end in December 

1998. Shorter time-series data are acceptable, however, if they meet certain criteria. For both the 

ESTIMATOR model and any trend test, the data set 

must contain a minimum of 10 years and 100 

“monthly” samples, or a mixture of monthly and 

quarterly data with at least 10 years and 75 samples with no date gaps greater than 3 months. 

Loads and trends were estimated on data sets for 

any time periods of 10 years or greater starting 

between January 1985 and January 1989 and continuing through December 1998. 

Data Analysis 

A brief description of the model used to estimate loads (ESTIMATOR), the statistical tests used 

to compute trends (linear regression, Seasonal 

Kendall, and Kendall-Theil), and procedures used 

with censored data are presented below. 

ESTIMATOR Model 

The loads of nutrients, suspended sediment, 

and total solids were estimated by use of the USGS 

7-para-meter, log-linear regression model (ESTIMATOR) developed by Cohn and others (1989). 

The model uses the Minimum Variance Unbiased 

Estimator (MVUE) developed by Bradu and 

Mundlak (1970) to correct for retransformation 

bias associated with log-linear regression. The 

adjusted maximum likelihood estimator (AMLE) 

(Cohn, 1988) is used to assign concentrations to 

censored data, which are data below a detectable 

limit. The model is of the form: 

In C = β + β ln[Q Q + β { ln[Q Q 2 [] ⁄ ] ⁄ ]} o 1 2 

+ β3[T T + 4[T T 2 – ] β – ]

+ β sin[2πT ] β + cos[2πT ] ε + , 5 6 

where ln is the natural logarithm function; 

C is measured concentration, in milligrams 

per liter; 

Q is measured streamflow, in cubic feet per 

second; 

T is time, measured in decimal years; 

Q and T are centering variables for streamflow 

and time; 

β are parameters estimated by ordinary least x 

squares (non-censored data) and minimum 

variance (censored data); and 

β0 is a constant; 

β1 and β2 describe the relation between 

concentration and flow; 

β3 and β4 describe the trend in concentration data; 

β5 and β6 describe seasonal variation in 

concentration data; and 

ε is combined independent random error, 

assumed to be normally distributed with 2 zero mean and variance σ . ε 

Linear Regression 

Linear regression is a parametric test that 

approximates the relation between two continuous 

variables. A linear trend is estimated by regressing 

a response variable (for example, flow or load) as a 

function of an explanatory variable (such as time). 

It is important that residual plots meet the assumptions of normality, constant variance, linearity, and 

independence. In most cases, data must be logtransformed in order to improve linearity. If this 

transformation is used, the residual plots again 

must be checked for normality, constant variance, 

linearity, and independence. When the assumptions are met, a null hypothesis of zero slope over 

time is tested. If the slope is significantly greater 

than zero, the null hypothesis is rejected, and the 

conclusion is that a linear trend over time has 

occurred. Because the regression model does not 

account for the error and dependence in the estimates, a conservative p-value of 0.01 or less was 

considered significant. The magnitude (percentage 

change over time) was estimated from the equation [e(b*t)-1] *100 where b is the slope and t is the 

time, in years. The upper and lower bounds, representing the 95-percent confidence interval around 

the magnitude, also were calculated. Helsel and 

Hirsch (1992) provide additional discussion for 

applying regression techniques to surface-water 

data. 

Seasonal Kendall Test 

The Seasonal Kendall (SK) test (Hirsch and 

others, 1982) is a nonparametric test for a monotonic linear trend that is resistant to outliers and is 

not dependent on the normality of the data set. By 

comparing only the data from similar seasons 

(monthly data used in the study), the test also 

reduces seasonal effects on concentrations when 

testing for trend. If the later value in time is larger, 

then a plus is recorded; if the later value in time is 

6 
smaller, then a minus is recorded. The test statistic 

is computed as the difference between the total 

number of pluses (increases in time) and the number of minuses (decreases in time). If the test statistic is 0, then there is no change (no trend) in time. 

As the test statistic increases or decreases from 0, 

the probability of a seasonal trend also increases. A 

p-value of 0.05 or less was considered significant. 

Kendall-Theil Trend Analysis

 The Kendall-Theil (KT) analysis is also a nonparametric test for a monotonic linear trend by use 

of pairwise comparison and a Kendall’s tau test for 

significance, similar to the SK test. The KT analysis 

differs from the SK test, however, in how it adjusts 

for seasonality. The SK test accounts for seasonality 

by calculating pairwise slopes on data within the 

same season; the overall trend slope is computed 

from the median of these seasonal slopes. The KT 

analysis accounts for seasonality by first obtaining 

residuals from an MVUE regression that includes 

seasonality terms. The trend slope is then determined by calculating pairwise slopes on the residual data for the entire period of study and 

computing the overall median of these slopes 

(Helsel and Hirsch, 1992). This approach allows 

increased power in the slope estimate for the KT 

test over the SK test. Flow-adjusted and seasonadjusted residuals from the ESTIMATOR model 

(with date terms B3 and B4 removed) were used as 

input to the KT analysis to estimate an adjusted 

trend in concentration. For censored data, a range 

in slope and magnitude was defined by twice computing the median slope—first, with censored data 

equal to zero, and second, with censored data 

equal to the maximum detection limit (Helsel and 

Hirsch, 1992). The magnitude was computed from 

the formula [bn/C-(bn/2)], where b is the slope, n 

is the number of data points, and C is the intercept 

(predicted concentration at center of flow) (Cohn 

and others, 1989). The upper and lower error 

bounds were calculated from the ranked slopes 

that correspond to the 95-percent confidence level. 

A p-value of 0.05 or less was considered significant. 

Detection and Trend Reporting 

of Censored Data 

The presence of a large number of censored 

values (values reported below the detection limit) 

in a data set can adversely affect the estimation of 

load and trend slope by not allowing for corrections because of variations in streamflow. In the 

ESTIMATOR model, values were assigned to the 

censored data by use of the AMLE (Cohn and others, 1989). 

The following decisions were presented to the 

Data Analysis Work Group (DAWG), a workgroup 

of the Monitoring Subcommittee of the Chesapeake Bay Program, and approved for use with the 

tests for trend. These decisions are based on current USGS computer program analysis (Shertz and 

others, 1991) and work by Helsel and Hirsch 

(1992). 

• <5 percent censored data – censored values 

will be assigned one half of the detection limit. 

For all trend tests, the p-value, the slope 

estimate, and the magnitude (percentage 

change over time) will be reported. 

• Between 5 and 20 percent censored data – three 

separate trend analysis tests of the data will be 

performed. First, on the raw data file with 

censored data set to half the detection limit 

(both KT and SK); second, all censored data set 

to 0 (KT only); and third, all censored data set 

to the detection limit (KT only). In these 

instances, the highest p-value, the range in 

slope estimate, and a range in the magnitude 

of the trend will be reported. 

• >20 percent censored data – trend results will 

not be reported. 

7 
TRENDS IN FLOW AND WATER-QUALITY
 

CONDITIONS
 

Trends in water quality were estimated by use 

of parametric and nonparametric statistical tests 

described earlier in this report. The parametric test 

involved a regression of nontransformed and 

transformed data with time. Nonparametric tests 

used nontransformed data and included the SK 

and KT. The SK test was used to estimate trends in 

streamflow and loads and was used to compare 

with linear regression trends. Analysis for trend 

was performed on the following: 

• monthly-mean flow 

• monthly load 

• flow-weighted concentrations (FWC), and 

• flow-adjusted concentrations (FAC) 

Each of the above trends provide a unique perspective on the changes in water quality within the 

Chesapeake Bay Watershed. These trends can be 

used to help document water-quality changes as a 

result of both natural and human-induced influences and can be used as indicators of improvement or lack of improvement of that quality within 

the Bay Watershed. 

Monthly-Mean Streamflow 

Trends in monthly-mean flows indicate the 

changes in hydrology (streamflow) over time. Fluctuations in streamflow affect the observed concentrations of nutrients and the average loads and 

concentrations of these constituents delivered to 

the tidal estuaries. Changes in streamflow also 

affect water quality and living-resource responses 

in the estuary. The trend in flow was calculated by 

use of a regression (log flow) with time. Trends 

were reported only for those sites where the residuals of the model met the assumptions of normality, constant variance, linearity, and independence. 

Significant upward trends in streamflow (fig. 2 

and Appendix 1) occurred at 12 sites. The sites are 

concentrated in the middle and lower areas of the 

Potomac River Basin, where significant flooding 

occurred in 3 of the last 4 years. None of the 30 

sites in the basin showed a downward trend in 

streamflow. For comparison, the SK test (monthly) 

also was performed at all sites, and where trends 

were significant by use of the SK, trends also were 

significant by use of the regression model. However, because parametric tests tend to have more 

power to detect trends than do nonparametric 

tests, some sites had not-significant trends by use 

of SK where the parametric test indicated a significant trend. In no cases did the results indicate 

trends in opposing directions. 

Monthly Load 

The constituent load is highly related to and 

dependent on flow. The load represents the 

amount of a given constituent transported and 

delivered downstream, eventually reaching the 

tidal estuaries. A trend in load will aid in explaining water-quality and living-resource changes in 

the tidal estuaries and assessing the effectiveness 

of Nutrient Reduction Strategies. Linear regression 

of log-transformed monthly loads from ESTIMATOR as a function of time was used to test for 

trend. In most cases, the regression produced normally distributed residuals. 

For nearly all constituents, load increased with 

flow. Where flow increased significantly, significant upward trends in TN load occurred at 6 of the 

12 sites (fig. 3) and NOx load trends were upward 

at 7 of the 12 sites (Appendix 1). The only downward trends in TN and NOx loads occurred at the 

Patuxent River Input site (site 11 on fig. 1). Significant upward trends in TP load occurred at 4 of the 

12 sites having upward trends in flow and, similar 

to the nitrogen, a downward trend in TP load 

occurred at the Patuxent River Input site (fig. 3). 

Results for DP loads, however, indicate downward 

trends at seven of the eight Susquehanna River 

sites (Appendix 1). In general, loads for TN and TP 

entering the Bay from the River Input Monitoring 

sites have increased from 1985 to 1998. 

In an average flow year, the three largest rivers 

draining to the Bay (the Susquehanna, the Potomac, and the James) deliver about 87 percent of the 

streamflow and about 96 percent of the nitrogen, 

91 percent of the phosphorus, and 93 percent of the 

suspended sediment or total solids loads into the 

Chesapeake Bay (Langland and others, 1995). During the period of study, flow for 3 of the last 4 years 

has exceeded the long-term average flow at the 

three largest rivers (fig. 4). 

Flow-Weighted Concentrations 

A trend in monthly flow-weighted concentrations represents a trend that is NOT adjusted for 

the effects of streamflow. This approach can be useful in comparing trends from nontidal sites to sites 

in the tidal tributaries and mainstem of the Bay. 

Monthly flow-weighted concentrations are calcu8 
Figure 2. Trends in streamflow, 1985-98. 

9 
Figure 3. Trends in load for total nitrogen and total phosphorus. 

10
 
1984 1987 1990 1993 1996 1999

YEAR 

0 

300 

50 

100 

150 

200 

250

DISCHARGE, IN MILLION OF GALLONS

0 

200,000 

50,000 

100,000 

150,000 

TOTAL NITROGEN, IN TONS 

STREAMFLOW 

TOTAL NITROGEN 

AVERAGE FLOW 1950-98 

AVERAGE LOAD 1988-98 

DISCHARGE, IN MILLIONS OF GALLONS

0 

300 

50 

100 

150 

200 

250 

0 

15,000 

5,000 

10,000 

STREAMFLOW 

TOTAL PHOSPHORUS 

AVERAGE FLOW 1950-98 

AVERAGE LOAD 1988-98 

1984 1987 1990 1993 1996 1999 

YEAR 

1984 1987 1990 1993 1996 1999

0 

300 

50 

100 

150 

200 

250

DISCHARGE, IN MILLIONS OF GALLONS

0 

15 

3 

6 

9 

12 

SEDIMENT, IN MILLIONS OF TONS 

STREAMFLOW 

SEDIMENT 

AVERAGE FLOW 1950-98 

AVERAGE LOAD 1988-98 

YEAR 

Figure 4. Combined annual flow and loads from the three largest rivers (Susquehanna, Potomac, 

and James) draining into the Chesapeake Bay Watershed for 1988-98 compared to long-term 

average flow (1950-98) and the average load (1988-98). 

TOTAL PHOSPHORUS, IN TONS 

11 
lated by dividing the total monthly load (from 

ESTIMATOR) by the monthly streamflow. Because 

ESTIMATOR uses the daily streamflow record, a 

daily concentration can be estimated and summed 

between sampling dates, and used to represent a 

“flow-weighted” monthly concentration, which 

may be more representative of the true monthly 

mean concentration. For example, in figure 5, the 

observed concentration of total nitrogen is 

1.0 mg/L, not weighted for flow. This is based on 

the one sample collected per month. When 

weighted for streamflow, however, the concentration (from ESTIMATOR) increases to 2.2 mg/L. It 

is important to account for the flow variability 

because the volume of flow occurring in short 

periods between sample intervals is likely to have 

a more pronounced and long-lived effect on average concentrations in the tidal estuaries and other 

mixed receiving areas. Therefore, a flow-weighted 

concentration should provide a more accurate estimate of the monthly mean concentration and may 

correlate better with trends in estuarine concentrations. Monthly flow-weighted concentrations were 

tested for trend by use of linear regressions. In 

most cases, the regression produced normally distributed residuals. In some cases, the trend was 

significant, with non-normal residuals. This precludes the use of linear regression. In these cases, 

the KT test was used (“Test” column in Appendix 

2). 

Trends for flow-weighted TN concentrations 

were downward at 13 sites distributed in nearly all 

10 major drainage basins (fig. 6 and Appendix 2). 

Trends for flow-weighted NOx concentrations 

were downward at five sites and were upward at 

six sites (Appendix 2). At only one of the six NOx 

sites with upward trends was the TN trend also 

upward. Trends in flow-weighted TP concentrations were downward at 16 sites (fig. 6). Data for 

one site, on the North Fork Shenandoah River, 

indicated an upward trend in TP. For TSS or SED, 

trends were upward at only two sites, one in the 

Patuxent River Basin, the other in the Potomac 

River Basin (Appendix 2). 

180 8 

STREAMFLOW 

TOTAL NITROGEN 

OBSERVED TN 

VALUE =1.0 mg/L 

FLOW-WEIGHTED TN 

VALUE = 2.2 mg/L 

5 10 15 20 25 

OCTOBER 1998 

7 

STEAMFLOW, IN CUBIC FEET PER SECOND 

TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER 

150 6 

5 

120 4 

3 

90 2 

1 

60 0 

Figure 5. Comparison between observed monthly concentration and a flow-weighted 

monthly concentration of total nitrogen. 

12 
Figure 6. Trends in flow-weighted concentrations for total nitrogen and total phosphorus. 

13
 
Flow-Adjusted Concentrations were not used in this report). The percentage difConcentrations of water-quality constituents 

are commonly correlated with streamflow. The 

cause of this relation varies between the 

constituent and the individual basin. For example, 

in point-source dominated basins, the input of 

many constituents is relatively constant. Increases 

in basin streamflow will most likely result in 

decreasing concentrations of these constituents as 

a result of dilution. In contrast, in nonpoint-source 

dominated basins, constituent concentrations 

entering the stream from overland flow will most 

likely increase as streamflow increases (Shertz and 

others, 1991). This flow-related variability must be 

removed to obtain flow independent water-quality 

concentrations that allow for examination of 

changes in water quality resulting from human 

activities. Flow-adjusted trends are the best 

indicator of human-induced changes affecting 

water quality within a watershed. To determine 

the trend in flow-adjusted concentration, observed 

concentration data were adjusted for season and 

streamflow by use of a 5-parameter ESTIMATOR 

model. This model is identical to the 7-parameter 

load model except the date and date-squared terms 

are removed. Values for multiple samples collected 

on the same day were averaged, and the resulting 

residual data set was input into the KT test. 

Results from the KT test indicate trends in TN 

and NOx concentration adjusted for flow were 

downward at 19 and 12 of the 30 sites, respectively, 

occurring in nearly all major Chesapeake Bay 

drainage basins (fig. 7 and Appendix 3). While 

only two sites had upward trends in TN, seven 

sites had upward trends in NOx. Trends in flowadjusted TP concentrations were downward at 21 

of the sites, with only 1 site showing an increase. 

The only significant upward trend for TSS or SED 

was in the Patuxent River Basin; trends were 

downward at five sites in Maryland and Virginia. 

As a result of flow and adjustment, an additional 

five TN and six TP sites indicated significant 

trends in concentration. 

In investigations from previous years (Langland and others, 1998), trends in flow-adjusted 

concentration were estimated by use of the date 

coefficient from the 7-parameter ESTIMATOR 

model. This method has been questioned because 

of perceived log-transformation bias. As a result of 

testing and comparing to other methods, the ESTIMATOR does appear to be valid for quantifying 

trends (although trend results from ESTIMATOR 

ferences between statistically significant trend 

magnitudes by use of the ESTIMATOR and KT are 

shown in figure 8. The median difference (absolute 

values) is about 7 percent for TN, 21 percent for 

NOx, 20 percent for TP, 12 percent for DP, and 

25 percent for SED/TSS. A total of 126 trend results 

were compared; 114 agreed in both significance 

and direction. There were no cases of opposing significant trends. 

STATUS OF FLOW 

AND WATER-QUALITY CONDITIONS 

Status is a measure of current water-quality 

conditions. In order to help facilitate comparison of 

current water-quality conditions among basins in 

the Chesapeake Bay Watershed, a mean annual 

yield (based on annual loads from ESTIMATOR 

divided by the drainage area) and a median flowweighted concentration were calculated at each of 

the 30 stations presented in this report. 

Mean Yield 

The “status” of current yields was assessed by 

station and constituent at the 30 sites in this study. 

As requested by DAWG, this “status” assessment 

was based on a 3-year mean of annual yield for the 

years 1996, 1997, and 1998 (if not available, then 

the last 3 years of record) and was determined as 

follows: 

1. Compile the 3-year yield data by station and 

constituent, 

2. Determine the 5th- and 95th-percentile for each 

constituent by use of available data from the 

30 sites, 

3. Subtract the 95th-percentile value from each 

status yield for each constituent, 

4. Subtract the 5th- and 95th-percentile values for 

each constituent, and 

5. Divide the result from (3) by the result from (4) 

and multiply by 100. 

The above procedure transforms the status 

yields of each constituent at the 30 sites into percentages between 0 and 100. The percentages were 

subtracted from 100 to allow a simple comparison 

between basins, because the lower the percentage, 

the lower the yield. Status yields and percentage 

for the 30 sites are presented in Appendix 1. As 

previously reported (Langland, 1995), the areas 

14 
Figure 7. Trends in flow-adjusted concentrations for total nitrogen and total phosphorus. 

15
 
100 

Outlier data value more than 3 times the 80 interquartile range outside the quartile 

Outlier data value less than or equal 

to 3 and more than 1.5 times the 

60 interquartile range outside the quartile 

Data value less than or equal to 1.5 times 

the interquartile range outside the quartile 

40 75th percentile 

Median 

25th percentile 

20 

0 

PERCENT DIFFERENCE 

TN NOx TP DP SED/TSS 

Figure 8. Percentage difference in statistically significant trends between the ESTIMATOR model and the 

Kendall-Theil test by use of absolute values. 

with the highest nitrogen yields also contain 

higher percentages of land in agriculture with 

some association to carbonate rock type; lower 

yields coincide with higher percentages of forest 

land. 

Median Concentration 

The “status” of current water-quality concentrations was determined by station and constituent 

at the 30 sites. This status was based on the median 

concentration for the period 1996-98 or the last 

3 years of record. The same procedure discussed 

above for status yields was used to compare 

median concentration. The status of the concentrations and percentages for the 30 sites are presented 

in Appendixes 2 and 3. Similar to the yields, the 

areas having the highest nitrogen concentrations 

also have higher percentages of land in agriculture; 

lower concentrations coincide with higher percentages of forest land. 

SUMMARY 

Nutrient and sediment data from 30 stream 

sites in nontidal portions of the Chesapeake Bay 

Watershed were analyzed to document annual 

loads and trends for the period 1985 through 1998, 

as part of an annual water-quality assessment for 

the Chesapeake Bay Program. Annual loads were 

estimated by use of the USGS ESTIMATOR model. 

Trends were estimated by use of log-transformed 

regressions, the Seasonal Kendall, or Kendall-Theil 

tests. Trends were reported for monthly-mean 

flow, monthly load, flow-weighted concentration, 

and flow-adjusted concentration. Mean yields and 

median flow-weighted concentrations based on the 

last 3 years of record were calculated to determine 

the status of recent water-quality conditions and 

help facilitate comparisons between basins. A significant upward trend in flow occurred at 12 of the 

30 sites. Increases in some nutrient and sediment 

loads and trends occurred at these same 12 sites. 

Throughout the Bay watershed, trends in flowadjusted and flow-weighted concentrations were 

generally downward or not significant for total 

nitrogen, not significant for nitrite plus nitrate 

nitrogen, and downward or not significant for 

phosphorus species. Flow-adjusted trends in concentration were downward at nearly all sites for 

sediment and dissolved solids in the Susquehanna 

and Potomac River Basins and were generally not 

significant in the Virginia river basins. 

16 
REFERENCES CITED Geological Survey and the Wisconsin 

Bradu, D., and Mundlak, Y., 1970, Estimation in 

log-normal linear models: Journal of the 

American Statistical Association, v. 65, no. 329, 

p. 198-211. 

Cohn, T.A., 1988, Adjusted maximum likelihood 

estimation of the moments of lognormal 

populations from type 1 censored samples: 

U.S. Geological Survey Open-File Report 88­

350, 34 p. 

Cohn, T.A., DeLong, L.L., Gilroy, E.J., Hirsch, R.M., 

and Wells, R.M., 1989, Estimating constituent 

loads: Water Resources Research, v. 25, no. 5, 

p. 937-942. 

Helsel, D.R., and Hirsch, R.M., 1992, Statistical 

methods in water resources: Amsterdam, 

Netherlands, Elsevier Science Publishers, 

Studies in Environmental Science, v. 49, 1992, 

522 p. 

Hirsch, R.M., Slack, J.R., and Smith, R.A., 1982, 

Techniques of trend analysis for monthly 

water-quality data: Water Resources Research, 

v. 18, no. 1, p. 107-121. 

Kammerer, P.A., Garn, H.S., Rasmussen, P.W., and 

Ball, J.R., 1998, A comparison of water-quality 

sample collection methods used by the U.S. 

Department of Natural Resources in 

Proceedings of the National Water-Quality 

Monitoring Council, National Conference on 

Monitoring, July 7-9, 1998, Reno, Nev.: 

Washington, D.C., U.S. Environmental 

Protection Agency, p. III-259-269. 

Langland, M.J., Lietman, P.L., and Hoffman, S.A., 

1995, A synthesis of nutrient and sediment 

data from watersheds within the Chesapeake 

Bay drainage basin: U.S. Geological Survey 

Water-Resources Investigations Report 95­

4233, 127 p. 

Langland, M.J., Edwards, R.E., and Darrell, L.C., 

1998, Status yields and trends of nutrient and 

sediment and methods of analysis for the 

nontidal data-collection programs, 

Chesapeake Bay Watershed 1985-96: U.S. 

Geological Survey Water-Resources 

Investigations Report 98-17, 60 p. 

Schertz, T.L., Alexander, R.B., and Ohe, D.J., 1991, 

The Computer Program Estimate Trend 

(ESTREND), A system for the detection of 

trends in water-quality data: U.S. Geological 

Survey Water-Resources Investigations Report 

91-4040, 63 p. 

17 
APPENDIX 1—TRENDS IN STREAMFLOW AND LOAD DATA 

FOR 9 RIVER INPUT MONITORING PROGRAM SITES AND 

21 MULTI-AGENCY NONTIDAL PROGRAM SITES IN THE 

CHESAPEAKE BAY WATERSHED 

Parameters: Q, streamflow; TN, total nitrogen; DNH, dissolved ammonia; TNH, total ammonia; NOx, total or 

dissolved nitrate, or, nitrite plus nitrate; DKN, dissolved ammonia plus organic nitrogen; TKN, total ammonia plus 

organic nitrogen; TP, total phosphorus; DP, dissolved phosphorus; DIP, dissolved inorganic phosphorus; TSS, total 

suspended solids; SED, suspended sediment. 

Station: flow, USGS streamflow site number; WQ, water-quality site number. 

Statistics: POR, time period used in test; test, regression (Reg), Kendall Theil (KT); log transformed; yes (Y) or no 

(N); p-value, measure of significance of regressor at 0.01; slope, regression slope; base median, median of first 

2 years of record; status median, median of last 3 years of record; magnitude, minimum (min) and maximum 

(max) percentage change in trend for indicated period of record; tend direction, UP, down (DN), or not significant 

(NS); relative rank, each individual status yield (pound per acre) compared to all others of the same parameter; 

shaded areas are significant at 99-percent confidence level; —, not applicable or insufficient data. 

18 
19 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

RIVER INPUT SITES 

01491000 - Choptank River near Greensboro, Md. (map ID site #9) 

Q 01491000 01491000 Jan85-Dec98 Reg Y 0.0004 95.8 — 40 

TN 01491000 01491000 Jan85-Dec98 Reg Y .0026 2.66 6.47 25 

TKN 01491000 01491000 Jan85-Dec98 Reg Y .3251 — — -23 

NOx 01491000 01491000 Jan85-Dec98 Reg Y .0001 1.60 3.60 51 

TP 01491000 01491000 Jan85-Dec98 Reg Y .0375 .086 .253 4 DP 01491000 01491000 Jan85-Dec98 Reg Y .0001 .024 .124 79 

DIP 01491000 01491000 Jan85-Dec98 Reg Y .0001 .020 .106 103 

SED 01491000 01491000 Jan85-Dec98 Reg Y .2553 9.87 31.8 -52 

01578310 - Susquehanna River at Conowingo, Md. (map ID site #8) 

Q 01578310 01578310 Jan85-Dec98 Reg Y .5522 29,700 — -20 

TN 01578310 01578310 Jan85-Dec98 Reg Y .4515 6.88 6.99 -37 

TKN 01578310 01578310 Jan85-Dec98 Reg Y .0001 — — -31 

NOx 01578310 01578310 Jan85-Dec98 Reg Y .4414 4.23 5.94 -18 

TP 01578310 01578310 Jan85-Dec98 Reg Y .0058 .205 .117 -17 

DP 01578310 01578310 Jan85-Dec98 Reg Y .0005 .087 .051 -29 

DIP 01578310 01578310 Jan85-Dec98 Reg Y .6533 .036 .050 -30 

SED 01578310 01578310 Jan85-Dec98 Reg Y .2673 47.0 55.1 -23 

 01594440 - Patuxent River near Bowie, Md. (map ID site #11) 

Q 01594440 01594440 Jan85-Dec98 Reg Y .0001 305 — 39 

TN 01594440 01594440 Jan85-Dec98 Reg Y .0001 8.52 8.31 -24 

TKN 01594440 01594440 Jan85-Dec98 Reg Y .0001 — — -25 

NOx 01594440 01594440 Jan85-Dec98 Reg Y .0001 5.63 5.30 -25 

TP 01594440 01594440 Jan85-Dec98 Reg Y .0001 .564 .487 -36 

DP 01594440 01594440 Jan85-Dec98 Reg Y .0001 .247 .152 -72 

DIP 01594440 01594440 Jan85-Dec98 Reg Y .0097 .185 .156 -7 

SED 01594440 01594440 Jan85-Dec98 Reg Y .7021 75.2 175 -51 
20 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01646580 - Potomac River at Chain Bridge, Md. (map ID site #28) 

Q 01646580 PR01 Jan85-Dec98 Reg Y 0.008 8,840 — 16 

TN 01646580 PR01 Jan85-Dec98 Reg Y .0170 3.28 11.0 12 

TKN 01646580 PR01 Jan85-Dec98 Reg Y .3638 — — -25 

NOx 01646580 PR01 Jan85-Dec98 Reg Y .0002 1.71 8.87 59 

TP 01646580 PR01 Jan85-Dec98 Reg Y .1957 .155 .402 -21 DP 01646580 PR01 Jan85-Dec98 Reg Y .6746 .090 .167 -35 

DIP 01646580 PR01 Jan85-Dec98 Reg Y .2682 .047 .128 -22 

SED 01646580 PR01 Jan85-Dec98 Reg Y .6131 49.2 125 -70 

 01668000 - Rappahannock River near Fredericksburg, Va. (map ID site #24) 

Q 01668000 01668000 Jan88-Dec98 Reg Y .1314 — — -11 

TN 01668000 01668000 Jan88-Dec98 Reg Y .6653 1.98 4.53 -44 NOx 01668000 01668000 Jan88-Dec98 Reg Y .9210 1.04 2.50 -56 TP 01668000 01668000 Jan88-Dec98 Reg Y .7623 .144 .383 -58 DIP 01668000 01668000 Jan88-Dec98 Reg Y .3115 .024 .068 -29 TSS 01668000 01668000 Jan88-Dec98 Reg Y .7115 60.7 187 -70 

 01673000 - Pamunkey River near Hanover, Va. (map ID site #25) 

Q 01673000 01673000 Jan89-Dec98 Reg Y .6040 — — -31 

TN 01673000 01673000 Jan89-Dec98 Reg Y .6918 2.14 2.23 -36 

NOx 01673000 01673000 Jan89-Dec98 Reg Y .0877 .647 1.02 -5 

TP 01673000 01673000 Jan89-Dec98 Reg Y .7414 .206 .214 -40 

DIP 01673000 01673000 Jan89-Dec98 Reg Y .0001 .044 .070 54 

TSS 01673000 01673000 Jan89-Dec98 Reg Y .6871 81.9 78.3 -72 

01674500 - Mattaponi River near Beulahville, Va. (map ID site #27) 

Q 01674500 01674500 Jan89-Dec98 Reg Y .1075 — — -9 TN 01674500 01674500 Jan89-Dec98 Reg Y .5434 2.24 1.70 -56 

NOx 01674500 01674500 Jan89-Dec98 Reg Y .3916 .383 .376 -53 

TP 01674500 01674500 Jan89-Dec98 Reg Y .3736 .113 .161 -61 

DIP 01674500 01674500 Jan89-Dec98 Reg Y .0907 .029 .056 -7 

TSS 01674500 01674500 Jan89-Dec98 Reg Y .9901 11.6 33.2 -59 
21 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

02035000 - James River at Cartersville, Va. (map ID site #29) 

Q 02035000 02035000 Jan88-Dec98 Reg Y 0.3386 — — -17 

TN 02035000 02035000 Jan88-Dec98 Reg Y .8483 1.66 1.93 -45 

NOx 02035000 02035000 Jan88-Dec98 Reg Y .5389 .630 .758 -53 TP 02035000 02035000 Jan88-Dec98 Reg Y .0611 .358 .291 -65 

DIP 02035000 02035000 Jan88-Dec98 Reg Y .0001 .258 .118 -50 

TSS 02035000 02035000 Jan88-Dec98 Reg Y .9823 41.6 122 -67 

 02041650 - Appomattox River at Matoaca, Va. (map ID site #30) 

Q 02041650 02041650 Jan89-Dec98 Reg Y .6742 — — -42 TN 02041650 02041650 Jan89-Dec98 Reg Y .2361 1.50 1.49 -55 

NOx 02041650 02041650 Jan89-Dec98 Reg Y .3779 .376 .401 -44 

TP 02041650 02041650 Jan89-Dec98 Reg Y .6605 .106 .138 -52 

DIP 02041650 02041650 Jan89-Dec98 Reg Y .5865 .029 .035 -28 

TSS 02041650 02041650 Jan89-Dec98 Reg Y .6403 22.8 27.3 -64 

MULTI-AGENCY SITES 

01531500 - Susquehanna River at Towanda, Pa. (map ID site #1) 

Q 01531500 TOW Jan89-Dec98 Reg N .9172 6,520 9,860 -35 TN 01531500 TOW Jan89-Dec98 Reg Y .0626 7.29 4.65 -61 

NOx 01531500 TOW Jan89-Dec98 Reg Y .0303 4.41 2.61 -64 

TP 01531500 TOW Jan89-Dec98 Reg Y .0238 .357 .230 -72 DP 01531500 TOW Jan89-Dec98 Reg Y .0001 .161 .082 -39 

DIP 01531500 TOW Jan89-Dec98 Reg Y .0300 .055 .029 -61 

SED 01531500 TOW Jan89-Dec98 Reg Y .2346 349 205 -77 

01540500 - Susquehanna River at Danville, Pa. (map ID site #2) 

Q 01540500 DAN Jan85-Dec98 Reg N .1750 11,000 14,600 -10 TN 01540500 DAN Jan85-Dec98 Reg Y .3286 5.70 4.77 -43 

NOx 01540500 DAN Jan85-Dec98 Reg Y .6540 2.79 2.99 -24 TP 01540500 DAN Jan85-Dec98 Reg Y .0309 .338 .197 -63 DP 01540500 DAN Jan85-Dec98 Reg Y .0001 .102 .055 -46 

DIP 01540500 DAN Jan85-Dec98 Reg Y .0870 .048 .031 -55 

SED 01540500 DAN Jan85-Dec98 Reg Y .4657 193 119 -122 
22 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01553500 - West Branch Susquehanna River at Lewisburg, Pa. (map ID site #3) 

Q 01553500 LEW Jan85-Dec98 Reg Y TN 01553500 LEW Jan85-Dec98 Reg Y NOx 01553500 LEW Jan85-Dec98 Reg Y 

0.5050 

.0875 .5225 

8,160 

5.85 2.98 

10,500 

4.13 2.86 

-20 -49 -35 

TP 01553500 LEW Jan85-Dec98 Reg Y .0008 .204 .094 -30 

DP 01553500 LEW Jan85-Dec98 Reg Y .0001 .129 .051 -52 

DIP 01553500 LEW Jan85-Dec98 Reg Y .0693 .049 .027 -47 SED 01553500 LEW Jan85-Dec98 Reg Y .7331 123 56.8 -66 

01567000 - Juniata River at Newport, Pa. (map ID site #4) 

Q 01567000 JUN Jan85-Dec98 Reg Y .0033 2,420 5,070 19 

TN 01567000 JUN Jan85-Dec98 Reg Y .4520 4.29 7.56 -22 

NOx 01567000 JUN Jan85-Dec98 Reg Y .1696 2.85 5.54 -11 TP 01567000 JUN Jan85-Dec98 Reg Y .0486 .196 .284 -59 

DP 01567000 JUN Jan85-Dec98 Reg Y .0015 .105 .115 -60 

DIP 01567000 JUN Jan85-Dec98 Reg Y .0246 .118 .061 -64 

SED 01567000 JUN Jan85-Dec98 Reg Y .4987 80.1 208 -62 

01576000 - Susquehanna River at Marietta, Pa. (map ID site #6) 

Q 01576000 MAR Jan85-Dec98 Reg Y .1388 25,500 40,000 -8 TN 01576000 MAR Jan85-Dec98 Reg Y .4052 4.96 6.27 -45 NOx 01576000 MAR Jan85-Dec98 Reg Y .9718 3.25 4.81 -34 TP 01576000 MAR Jan85-Dec98 Reg Y .1047 .196 .200 -73 

DP 01576000 MAR Jan85-Dec98 Reg Y .0008 .095 .080 -26 

DIP 01576000 MAR Jan85-Dec98 Reg Y .0121 .021 .039 15 

SED 01576000 MAR Jan85-Dec98 Reg Y .6001 84.0 117 -93 
23 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01576754 - Conestoga River at Conestoga, Pa. (map ID site #7) 

Q 01576754 CON Jan85-Dec98 Reg Y 0.0529 451 747 0 

TN 01576754 CON Jan85-Dec98 Reg Y .5246 26.7 37.5 -16 

NOx 01576754 CON Jan85-Dec98 Reg Y .2683 19.7 30.5 -10 

TP 01576754 CON Jan85-Dec98 SK N .2305 1.67 1.45 -61 

DP 01576754 CON Jan85-Dec98 Reg Y .0001 .955 .608 -40 

DIP 01576754 CON Jan85-Dec98 Reg Y .0001 .905 .536 -39 

SED 01576754 CON Jan85-Dec98 Reg Y .5241 337 452 -138 

01570000 - Conodoguinet Creek near Hogestown, Pa. (map ID site #5) 

Q 01570000 WQN0213 Jan85-Dec98 Reg Y .0001 — — 59 

TN 01570000 WQN0213 Jan85-Dec98 Reg Y .0001 7.44 20.1 84 

NOx 01570000 WQN0213 Jan85-Dec98 — — — — — — TP 01570000 WQN0213 Jan85-Dec98 Reg Y .4076 .047 .251 -70 DP 01570000 WQN0213 Jan85-Dec98 Reg Y .0015 .034 .088 -72 

DIP 01570000 WQN0213 Jan85-Dec98 Reg Y .0001 .224 .066 -60 

TSS 01570000 WQN0213 Jan85-Dec98 — — — — — — 

01586000 - North Branch Patapsco River at Cedarhurst, Md. (map ID site #12) 

Q 01586000 NPA0165 Jan85-Dec98 Reg Y .0001 — — 30 

TN 01586000 NPA0165 Jan85-Dec98 Reg Y .0001 8.69 22.5 75 

TKN 01586000 NPA0165 Jan85-Dec98 Reg Y .6894 — — -45 

NOx 01586000 NPA0165 Jan85-Dec98 Reg Y .0001 7.24 16.5 60 

TP 01586000 NPA0165 Jan85-Dec98 Reg Y .7424 .120 .236 -55 DP 01586000 NPA0165 Jan85-Dec98 — — — — — — DIP 01586000 NPA0165 Jan85-Dec98 — — — — — — TSS 01586000 NPA0165 Jan85-Dec98 Reg Y .0672 17.6 72.7 -7 
24 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01592500 - Patuxent River near Laurel, Md. (map ID site #10) 

Q 01592500 PXT0809 Jan85-Dec98 Reg Y 0.0039 — — 26 

TN 01592500 PXT0809 Jan85-Dec98 Reg Y .0006 0.622 6.68 49 

TKN 01592500 PXT0809 Jan85-Dec98 Reg Y .0018 — — 35 

NOx 01592500 PXT0809 Jan85-Dec98 Reg Y .0008 .352 4.02 46 

TP 01592500 PXT0809 Jan85-Dec98 Reg Y .0079 .023 .122 -6 

DP 01592500 PXT0809 Jan85-Dec98 — — — — — — DIP 01592500 PXT0809 Jan85-Dec98 — — — — — — TSS 01592500 PXT0809 Jan85-Dec98 Reg Y .0001 3.27 32.1 139 

01599000 - Georges Creek near Franklin, Md. (map ID site #13) 

Q 01599000 GEO0009 Jan85-Dec98 Reg Y .1633 — — -11 TN 01599000 GEO0009 Jan85-Dec98 Reg Y .6263 3.65 5.08 -40 

TKN 01599000 GEO0009 Jan85-Dec98 Reg Y .2113 — — -52 NOx 01599000 GEO0009 Jan85-Dec98 — — — — — — 

TP 01599000 GEO0009 Jan85-Dec98 Reg Y .1684 .178 .214 -48 

DP 01599000 GEO0009 Jan85-Dec98 — — — — — — 

DIP 01599000 GEO0009 Jan85-Dec98 — — — — — — 

TSS 01599000 GEO0009 Jan85-Dec98 Reg Y .0491 45.9 165 1 

01601500 - Wills Creek near Cumberland, Md. (map ID site #14) 

Q 01601500 WIL0013 Jan85-Dec98 Reg Y .0178 — — -17 TN 01601500 WIL0013 Jan85-Dec98 Reg Y .4155 3.84 5.37 -57 

DNH 01601500 WIL0013 Jan85-Dec98 Reg Y .0105 — — 19 

TKN 01601500 WIL0013 Jan85-Dec98 Reg Y .1659 — — -60 NOx 01601500 WIL0013 Jan85-Dec98 — — — — — — TP 01601500 WIL0013 Jan85-Dec98 Reg Y .2805 .077 .195 -14 

DP 01601500 WIL0013 Jan85-Dec98 — — — — — — DIP 01601500 WIL0013 Jan85-Dec98 — — — — — — TSS 01601500 WIL0013 Jan85-Dec98 Reg Y .2999 31.4 76.3 -32 
25 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01610000 - Potomac River at Paw Paw, W. Va. (map ID site #15) 

Q 01610000 POT2766 Jan85-Dec98 Reg TN 01610000 POT2766 Jan85-Dec98 Reg 

Y Y 

0.2156 

.6821 

— 

2.89 

— 

4.14 

-12 -28 

DNH 01610000 POT2766 Jan85-Dec98 Reg Y .001 — — -17 

TKN 01610000 POT2766 Jan85-Dec98 Reg Y .3641 — — -49 

NOx 01610000 POT2766 Jan85-Dec98 — — — — — — TP 01610000 POT2766 Jan85-Dec98 Reg Y .4333 .145 .169 -56 DP 01610000 POT2766 Jan85-Dec98 — — — — — — DIP 01610000 POT2766 Jan85-Dec98 — — — — — — TSS 01610000 POT2766 Jan85-Dec98 Reg Y .7989 30.2 82.3 -52 

01613000 - Potomac River at Hancock, Md. (map ID site #16) 

Q 01613000 POT2386 Jan85-Dec98 Reg Y .1999 — — -12 TN 01613000 POT2386 Jan85-Dec98 Reg Y .3762 3.11 4.04 -46 

TNH 01613000 POT2386 Jan85-Dec98 Reg Y .8974 — — -42 TKN 01613000 POT2386 Jan85-Dec98 Reg Y .0262 — — -59 NOx 01613000 POT2386 Jan85-Dec98 Reg Y .487 1.68 2.38 -49 TP 01613000 POT2386 Jan85-Dec98 Reg Y .2826 .133 .188 -57 

DP 01613000 POT2386 Jan85-Dec98 — — — — — — DIP 01613000 POT2386 Jan85-Dec98 — — — — — — TSS 01613000 POT2386 Jan85-Dec98 Reg Y .1449 27.4 94.9 -21 

01614500 - Conococheague Creek at Fairview, Md. (map ID site #17) 

Q 01614500 CON0180 Jan85-Dec98 Reg Y .0001 — — 44 

TN 01614500 CON0180 Jan85-Dec98 Reg Y .0021 8.64 24.1 22 

DNH 01614500 CON0180 Jan85-Dec98 Reg Y .8734 — — -37 TKN 01614500 CON0180 Jan85-Dec98 Reg Y .5315 — — -26 NOx 01614500 CON0180 Jan85-Dec98 Reg Y .0052 7.43 19.2 16 

TP 01614500 CON0180 Jan85-Dec98 Reg Y .8049 .332 .524 -26 DP 01614500 CON0180 Jan85-Dec98 — — — — — — 

DIP 01614500 CON0180 Jan85-Dec98 — — — — — — 

TSS 01614500 CON0180 Jan85-Dec98 Reg Y .0064 17.0 175 42 
26 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01638500 - Potomac River at Point of Rocks, Md. (map ID site #19) 

Q 01638500 POT1595 Jan85-Dec98 Reg Y 0.0073 — — 14 

TN 01638500 POT1595 Jan85-Dec98 Reg Y .0893 4.38 8.60 -4 

DNH 01638500 POT1595 Jan85-Dec98 Reg Y .7494 — — -46 

TKN 01638500 POT1595 Jan85-Dec98 Reg Y .9512 — — -35 

NOx 01638500 POT1595 Jan85-Dec98 Reg Y .0666 2.72 5.89 -2 

TP 01638500 POT1595 Jan85-Dec98 Reg Y .8323 .165 .293 -40 

DP 01638500 POT1595 Jan85-Dec98 — — — — — — DIP 01638500 POT1595 Jan85-Dec98 — — — — — — TSS 01638500 POT1595 Jan85-Dec98 Reg Y .0616 27.0 117 -4 

01643000 - Monocacy River at Reels Mill Road, Md. (map ID site #18) 

Q 01643000 MON0528 Jan85-Dec98 Reg Y .0121 — — 12 

TN 01643000 MON0528 Jan85-Dec98 Reg Y .5954 5.45 11.0 -5 DNH 01643000 MON0528 Jan85-Dec98 Reg Y .5601 — — -41 TKN 01643000 MON0528 Jan85-Dec98 Reg Y .5604 — — -47 NOx 01643000 MON0528 Jan85-Dec98 Reg Y .0265 2.53 3.68 -75 

TP 01643000 MON0528 Jan85-Dec98 Reg Y .6093 .285 .524 -49 

DP 01643000 MON0528 Jan85-Dec98 — — — — — — DIP 01643000 MON0528 Jan85-Dec98 — — — — — — TSS 01643000 MON0528 Jan85-Dec98 Reg Y .0728 18.9 82.7 -5 

01631000 - S. Fork Shenandoah River near Front Royal, Va. (map ID site #20) 

Q 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .0006 — — 32 

TN 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .9501 2.21 4.41 -41 TNH 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .3919 — — -57 

TKN 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .0169 — — -70 

NOx 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .002 1.48 4.92 31 

TP 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .3178 .361 .599 -19 DP 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — DIP 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — TSS 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — 
27 

Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

01634000 - N. Fork Shenandoah River near Strasburg, Va. (map ID site #21) 

Q 01634000 1BNFS010.34 Jan85-Dec98 Reg Y 0.0003 — — 43 

TN 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .0001 1.55 7.48 96 

TNH 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .1249 — — -13 TKN 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .563 — — -35 NOx 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .0001 1.15 7.61 142 

TP 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .0001 .143 .540 169 

DP 01634000 1BNFS010.34 Jan85-Dec98 — — — — — — 

DIP 01634000 1BNFS010.34 Jan85-Dec98 — — — — — — 

TSS 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .0107 5.19 38.7 48 1

01666500 - Robinson River near Locust Dale, Va. (map ID site #23) 

Q 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0004 — — 40 

TN 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .22 1.45 3.11 -18 TNH 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .2349 — — -66 

TKN 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .4427 — — -33 NOx 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0583 1.16 2.79 -1 

TP 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0014 .191 .505 39 

DP 01666500 3-ROB001.90 Jan85-Dec98 — — — — — — 

DIP 01666500 3-ROB001.90 Jan85-Dec98 — — — — — — 

TSS 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0014 12.4 95.3 

01671020 - North Anna River at Hart Corner near Doswell, Va. (map ID site #26) 

Q 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .0456 — — 1 

TN 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .4572 .434 1.34 -2 

TNH 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .4189 — — -29 TKN 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .7159 — — -43 NOx 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .1975 .243 .623 -18 

TP 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .661 .178 .205 -43 

DP 01671020 8-NAR005.42 Jan85-Dec98 — — — — — — DIP 01671020 8-NAR005.42 Jan85-Dec98 — — — — — — TSS 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .0573 5.77 22.8 -2 
Appendix 1. Trends in streamflow and load data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Program sites 

Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median yields Status-median yields Magnitud

Minimum Ma

02013100 - Jackson River below Dunlap Creek at Covington, Va. (map ID site #28) 

Q 02013100 2-JKS023.61 Jan85-Dec98 Reg Y TN 02013100 2-JKS023.61 Jan85-Dec98 Reg Y 

0.1632 

.4438 

— 

0.916 

— 

1.36 

-8 

-15 

TNH 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0073 — — 9 

TKN 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0659 — — -35 NOx 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0466 .257 .815 1 

TP 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0001 5.18 1.16 -83 

DP 02013100 2-JKS023.61 Jan85-Dec98 — — — — — — DIP 02013100 2-JKS023.61 Jan85-Dec98 — — — — — — TSS 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .1306 13.2 24.5 -9 

28 
APPENDIX 2—TRENDS IN FLOW-WEIGHTED CONCENTRATION 

DATA FOR 9 RIVER INPUT MONITORING PROGRAM SITES AND 

21 MULTI-AGENCY NONTIDAL PROGRAM SITES IN THE 

CHESAPEAKE BAY WATERSHED 

Parameters: TN, total nitrogen; DNH, dissolved ammonia; TNH, total ammonia; NOx, total or dissolved nitrate, or, 

nitrite plus nitrate; DKN, dissolved ammonia plus organic nitrogen; TKN, total ammonia plus organic nitrogen; TP, 

total phosphorus; DP, dissolved phosphorus; DIP, dissolved inorganic phosphorus; TSS, total suspended solids; 

SED, suspended sediment. 

Station: flow, USGS discharge site number; WQ, water-quality site number. 

Statistics: POR, time period used in test; test, regression (Reg), Kendall Theil (KT); log transformed; yes (Y) or no 

(N); p-value, measure of significance of regressor at 0.01; slope, regression slope; base median, median of first 

2 years of record; status median, median of last 3 years of record; magnitude, minimum (min) and maximum 

(max) percentage change in trend for indicated period of record; tend direction, UP, down (DN), or not significant 

(NS); relative rank, each individual status concentration (milligrams per liter) compared to all others of the same 

parameter; shaded areas are significant at 99-percent confidence level; —, not applicable or insufficient data. 

29 
30 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

RIVER INPUT SITE DATA 

01491000 - Choptank River near Greensboro, Md. (map ID site #9) 

TN 01491000 01491000 Jan85-Dec98 KT Y 0.0001 1.72 1.56 -6 

NOx 01491000 01491000 Jan85-Dec98 Reg N .5678 1.01 .965 -6 TKN 01491000 01491000 Jan85-Dec98 Reg Y .0001 — — -29 -

TP 01491000 01491000 Jan85-Dec98 Reg Y .1702 .056 .057 -26 DP 01491000 01491000 Jan85-Dec98 Reg Y .0001 .019 .029 27 

DIP 01491000 01491000 Jan85-Dec98 Reg Y .0001 .014 .024 42 SED 01491000 01491000 Jan85-Dec98 Reg Y .0784 6.02 9.02 -48 

01578310 - Susquehanna River at Conowingo, Md. (map ID site #8) 

TN 01578310 01578310 Jan85-Dec98 Reg N .0001 1.93 1.62 -19 -

NOx 01578310 01578310 Jan85-Dec98 Reg N .0454 1.19 1.21 1 TKN 01578310 01578310 Jan85-Dec98 Reg Y .0001 — — -52 -

TP 01578310 01578310 Jan85-Dec98 KT Y .0001 .060 .032 -57 -DP 01578310 01578310 Jan85-Dec98 Reg Y .0001 .024 .012 -53 -DIP 01578310 01578310 Jan85-Dec98 Reg N .6223 .009 .009 -14 SED 01578310 01578310 Jan85-Dec98 Reg Y .1155 13.4 13.6 -6 

 01594440 - Patuxent River near Bowie, Md. (map ID site #11) 

TN 01594440 01594440 Jan85-Dec98 Reg Y .0001 4.76 1.77 -63 -

NOx 01594440 01594440 Jan85-Dec98 Reg Y .0001 3.24 1.21 -61 -

TKN 01594440 01594440 Jan85-Dec98 Reg Y .0001 — — -67 -

TP 01594440 01594440 Jan85-Dec98 Reg Y .0001 .329 .114 -72 -DP 01594440 01594440 Jan85-Dec98 Reg Y .0001 .143 .041 -72 -DIP 01594440 01594440 Jan85-Dec98 Reg Y .0001 .105 .042 -50 -SED 01594440 01594440 Jan85-Dec98 Reg Y .0001 45.6 38.0 -31 -
31 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

01646580 - Potomac River at Chain Bridge, Md. (map ID site #28) 

TN 01646580 PR01 Jan85-Dec98 Reg Y 0.2125 1.79 2.09 -4 

NOx 01646580 PR01 Jan85-Dec98 Reg N .0001 .978 1.48 28 

TKN 01646580 PR01 Jan85-Dec98 Reg Y .0036 — — -9 -

TP 01646580 PR01 Jan85-Dec98 Reg Y .6033 .099 .100 -33 DP 01646580 PR01 Jan85-Dec98 Reg Y .0001 .054 .041 -22 -

DIP 01646580 PR01 Jan85-Dec98 Reg Y .0165 .030 .025 -32 

 01668000 - Rappahannock River near Fredericksburg, Va. (map ID site #24) 

TSS 01668000 01668000 Jan88-Dec98 Reg Y .8476 25.8 41.6 -67 1

TN 01668000 01668000 Jan88-Dec98 Reg Y .0934 .959 .999 -38 NOx 01668000 01668000 Jan88-Dec98 Reg N .0570 .544 .498 -36 TP 01668000 01668000 Jan88-Dec98 Reg Y .4219 .068 .080 -54 DIP 01668000 01668000 Jan88-Dec98 Reg Y .9006 .012 .014 -21 

 01673000 - Pamunkey River near Hanover, Va. (map ID site #25) 

TSS 01673000 01673000 Jan89-Dec98 Reg Y .2302 28.9 25.4 -60 

TN 01673000 01673000 Jan89-Dec98 Reg Y .5426 .740 .697 -8 SED 01646580 PR01 Jan85-Dec98 Reg Y .0080 32.3 34.8 -19 -

NOx 01673000 01673000 Jan89-Dec98 Reg N .0001 .236 .305 26 

TP 01673000 01673000 Jan89-Dec98 Reg Y .5659 .075 .067 -13 

01674500 - Mattaponi River near Beulahville, Va. (map ID site #27) 

TSS 01674500 01674500 Jan89-Dec98 Reg N .7662 8.10 9.69 -22 

DIP 01673000 01673000 Jan89-Dec98 Reg Y .0001 .016 .025 74 1

TN 01674500 01674500 Jan89-Dec98 Reg Y .0001 .841 .521 -22 -

NOx 01674500 01674500 Jan89-Dec98 Reg N .0001 .201 .127 -28 -TP 01674500 01674500 Jan89-Dec98 KT N .0001 .082 .045 -31 -DIP 01674500 01674500 Jan89-Dec98 Reg N .0001 .020 .017 23 
32 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

02035000 - James River at Cartersville, Va. (map ID site #29) 

TSS 02035000 02035000 Jan88-Dec98 Reg Y 0.6124 15.5 34.0 -60 

TN 02035000 02035000 Jan88-Dec98 Reg Y .0169 .624 .587 -34 

NOx 02035000 02035000 Jan88-Dec98 Reg Y .0031 .239 .227 -12 -

TP 02035000 02035000 Jan88-Dec98 KT N .0000 .154 .088 -48 -

DIP 02035000 02035000 Jan88-Dec98 Reg Y .0001 .098 .035 -60 -

 02041650 - Appomattox River at Matoaca, Va. (map ID site #30)
 

TSS 02041650 02041650 Jan89-Dec98 Reg Y .6085 9.19 9.18 -38 

TN 02041650 02041650 Jan89-Dec98 Reg Y .0001 .594 .500 -14 -

NOx TP 

02041650 02041650 

02041650 02041650 

Jan89-Dec98 Jan89-Dec98 

Reg Reg 

Y Y 

.0817 .6620 

.171 .043 

.162 .046 

-16 -18 

MULTI-AGENCY SITE DATA 

01531500 - Susquehanna River at Towanda, Pa. (map ID site #1) 

TN 01531500 TOW Jan89-Dec98 Reg NOx 01531500 TOW Jan89-Dec98 Reg TP 01531500 TOW Jan89-Dec98 Reg 

Y Y Y 

.1364 .0858 .0551 

2.45 1.55 

.135 

.965 .531 .050 

-68 -70 -76 

DIP 02041650 02041650 Jan89-Dec98 Reg N .0001 .011 .013 20 

DP 01531500 TOW Jan89-Dec98 Reg Y .0026 .062 .019 -30 -

DIP 01531500 TOW Jan89-Dec98 Reg Y .1012 .020 .007 -68 SED 01531500 TOW Jan89-Dec98 Reg Y .2516 137 46.0 -79 

01540500 - Susquehanna River at Danville, Pa. (map ID site #2) 

TN 01540500 DAN Jan85-Dec98 Reg Y .0870 2.00 1.16 -60 NOx 01540500 DAN Jan85-Dec98 Reg Y .5176 1.08 .707 -47 

TP 01540500 DAN Jan85-Dec98 Reg Y .0082 .117 .053 -18 -

DP 01540500 DAN Jan85-Dec98 Reg Y .0001 .038 .013 -46 -

DIP 01540500 DAN Jan85-Dec98 Reg Y .0245 .019 .008 -68 SED 01540500 DAN Jan85-Dec98 Reg Y .2094 82.4 27.7 -74 
33 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

01553500 - West Branch Susquehanna River at Lewisburg, Pa. (map ID site #3) 

TN 01553500 LEW Jan85-Dec98 Reg Y NOx 01553500 LEW Jan85-Dec98 Reg Y 

0.0608 

.3050 

1.16 

.612 

0.99 

.562 

-59 -48 

TP 01553500 LEW Jan85-Dec98 Reg Y .0007 .047 .026 -34 -

DP 01553500 LEW Jan85-Dec98 Reg Y .0001 .025 .010 -54 -DIP 01553500 LEW Jan85-Dec98 Reg Y .0670 .011 .007 -58 SED 01553500 LEW Jan85-Dec98 Reg Y .5425 25.5 15.5 -67 

01567000 - Juniata River at Newport, Pa. (map ID site #4) 

TN 01567000 JUN Jan85-Dec98 Reg Y .1431 1.94 1.18 -56 

NOx 01567000 JUN Jan85-Dec98 Reg Y .3235 1.24 .911 -50 TP 01567000 JUN Jan85-Dec98 Reg Y .0003 .078 .036 -36 -DP 01567000 JUN Jan85-Dec98 Reg Y .0001 .046 .018 -47 -DIP 01567000 JUN Jan85-Dec98 Reg Y .0001 .042 .014 -42 -SED 01567000 JUN Jan85-Dec98 Reg Y .5377 40.2 28.3 -64 

01576000 - Susquehanna River at Marietta, Pa. (map ID site #6) 

TN 01576000 MAR Jan85-Dec98 Reg Y .0794 2.15 1.04 -61 NOx 01576000 MAR Jan85-Dec98 Reg Y .2664 1.29 .813 -54 

TP 01576000 MAR Jan85-Dec98 Reg Y .0186 .084 .035 -73 -DP 01576000 MAR Jan85-Dec98 Reg Y .0001 .040 .014 -38 -

DIP 01576000 MAR Jan85-Dec98 Reg Y .2360 .008 .008 -19 1SED 01576000 MAR Jan85-Dec98 Reg Y .2564 35.1 23.0 -74 

01576754 - Conestoga River at Conestoga, Pa. (map ID site #7) 

TN 01576754 CON Jan85-Dec98 Reg Y .2686 10.1 5.76 -39 

NOx 01576754 CON Jan85-Dec98 Reg Y .3912 7.14 4.67 -35 TP 01576754 CON Jan85-Dec98 Reg Y .0013 .690 .237 -27 -

DP 01576754 CON Jan85-Dec98 Reg Y .0001 .343 .101 -52 -DIP 01576754 CON Jan85-Dec98 Reg Y .0001 .321 .095 -52 -SED 01576754 CON Jan85-Dec98 Reg Y .1896 124 92.1 -72 
34 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

01570000 - Conodoguinet Creek near Hogestown, Pa. (map ID site #5) 

TN 01570000 WQN0213 Jan85-Dec98 Reg N 0.5412 2.38 2.65 -36 

NOx 01570000 WQN0213 Jan85-Dec98 — — — — — — TP 01570000 WQN0213 Jan85-Dec98 Reg Y .0045 .078 .028 -34 -

DP 01570000 WQN0213 Jan85-Dec98 Reg Y .0001 .046 .012 -72 -DIP 01570000 WQN0213 Jan85-Dec98 Reg N .0001 .104 .009 -69 -TSS 01570000 WQN0213 Jan85-Dec98 — — — — — — 

01586000 - North Branch Patapsco River at Cedarhurst, Md. (map ID site #12) 

TN 01586000 NPA0165 Jan85-Dec98 Reg Y .2419 3.57 4.51 25 

NOx 01586000 NPA0165 Jan85-Dec98 Reg N .0001 2.96 3.37 10 

TP 01586000 NPA0165 Jan85-Dec98 Reg Y .143 .066 .047 -67 DP 01586000 NPA0165 Jan85-Dec98 — — — — — — DIP 01586000 NPA0165 Jan85-Dec98 — — — — — — TSS 01586000 NPA0165 Jan85-Dec98 Reg Y .2419 10.2 17.7 -31 

01592500 - Patuxent River near Laurel, Md. (map ID site #10) 

TN 01592500 PXT0809 Jan85-Dec98 Reg N .0001 1.55 1.92 18 

NOx 01592500 PXT0809 Jan85-Dec98 Reg N .0001 .942 1.15 16 

TP 01592500 PXT0809 Jan85-Dec98 Reg N .0001 .045 .043 -4 DP 01592500 PXT0809 Jan85-Dec98 — — — — — — 

DIP 01592500 PXT0809 Jan85-Dec98 — — — — — — TSS 01592500 PXT0809 Jan85-Dec98 Reg Y .0001 6.88 12.0 87 

01599000 - Georges Creek near Franklin, Md. (map ID site #13) 

TN 01599000 GEO0009 Jan85-Dec98 Reg N .0001 2.00 1.37 -31 -

NOx 01599000 GEO0009 Jan85-Dec98 — — — — — — 

TP 01599000 GEO0009 Jan85-Dec98 Reg Y .0001 .112 .063 -36 -

DP 01599000 GEO0009 Jan85-Dec98 — — — — — — 

DIP 01599000 GEO0009 Jan85-Dec98 — — — — — — TSS 01599000 GEO0009 Jan85-Dec98 Reg Y .0012 29.9 39.1 13 
35 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

01601500 - Wills Creek near Cumberland, Md. (map ID site #14) 

TN 01601500 WIL0013 Jan85-Dec98 Reg Y 0.0001 1.71 1.20 -28 -

NOx 01601500 WIL0013 Jan85-Dec98 — — — — — — 

TP 01601500 WIL0013 Jan85-Dec98 Reg N .2579 .038 .043 -22 DP 01601500 WIL0013 Jan85-Dec98 — — — — — — DIP 01601500 WIL0013 Jan85-Dec98 — — — — — — TSS 01601500 WIL0013 Jan85-Dec98 Reg Y .3966 14.0 18.9 -22 

01610000 - Potomac River at Paw Paw, W. Va. (map ID site #15) 

TN 01610000 POT2766 Jan85-Dec98 Reg Y .0001 1.17 1.08 -8 -

NOx 01610000 POT2766 Jan85-Dec98 — — — — — — 

TP 01610000 POT2766 Jan85-Dec98 Reg Y .0011 .078 .052 -21 -

DP 01610000 POT2766 Jan85-Dec98 — — — — — — 

DIP 01610000 POT2766 Jan85-Dec98 — — — — — — TSS 01610000 POT2766 Jan85-Dec98 Reg Y .6483 13.0 19.4 -46 

01613000 - Potomac River at Hancock, Md. (map ID site #16) 

TN 01613000 POT2386 Jan85-Dec98 Reg Y .0001 1.37 1.05 -30 -

NOx 01613000 POT2386 Jan85-Dec98 Reg Y .0001 .721 .565 -21 -TP 01613000 POT2386 Jan85-Dec98 Reg N .0001 .077 .047 -18 -DP 01613000 POT2386 Jan85-Dec98 — — — — — — 

DIP 01613000 POT2386 Jan85-Dec98 — — — — — — TSS 01613000 POT2386 Jan85-Dec98 Reg Y .1246 12.0 22.9 -12 1

01614500 - Conococheague Creek at Fairview, Md. (map ID site #17) 

TN 01614500 CON0180 Jan85-Dec98 Reg N .0001 4.72 4.16 -12 -

NOx 01614500 CON0180 Jan85-Dec98 Reg N .0001 3.79 3.27 -14 -

TP 01614500 CON0180 Jan85-Dec98 Reg N .0001 .182 .118 -43 -DP 01614500 CON0180 Jan85-Dec98 — — — — — — 

DIP 01614500 CON0180 Jan85-Dec98 — — — — — — TSS 01614500 CON0180 Jan85-Dec98 Reg N .0395 13.8 26.5 7 2
36 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

01638500 - Potomac River at Point of Rocks, Md. (map ID site #19) 

TN 01638500 POT1595 Jan85-Dec98 Reg Y 0.0001 2.14 1.89 -11 -

NOx 01638500 POT1595 Jan85-Dec98 Reg N .0061 1.28 1.22 -4 -TP 01638500 POT1595 Jan85-Dec98 Reg Y .0012 .108 .079 -16 -DP 01638500 POT1595 Jan85-Dec98 — — — — — — 

DIP 01638500 POT1595 Jan85-Dec98 — — — — — — TSS 01638500 POT1595 Jan85-Dec98 Reg Y .1856 13.7 32.6 -17 1

01643000 - Monocacy River at Reels Mill Road, Md. (map ID site #18) 

TN 01643000 MON0528 Jan85-Dec98 Reg Y .0001 2.80 1.84 -37 -

NOx 01643000 MON0528 Jan85-Dec98 Reg N .0001 1.27 .614 -37 -TP 01643000 MON0528 Jan85-Dec98 Reg N .0001 .219 .126 -32 -DP 01643000 MON0528 Jan85-Dec98 — — — — — — 

DIP 01643000 MON0528 Jan85-Dec98 — — — — — — TSS 01643000 MON0528 Jan85-Dec98 Reg Y .3846 15.6 18.8 -18 

01631000 - S. Fork Shenandoah River near Front Royal, Va. (map ID site #20) 

TN 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .0001 1.23 1.09 -16 -

NOx 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .0001 .758 1.21 62 

TP 01631000 1BSSF003.56 Jan85-Dec98 Reg Y .0001 .215 .182 -11 -DP 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — DIP 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — TSS 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — 

01634000 - N. Fork Shenandoah River near Strasburg, Va. (map ID site #21) 

TN 01634000 1BNFS010.34 Jan85-Dec98 Reg N .0001 1.20 1.73 19 

NOx 01634000 1BNFS010.34 Jan85-Dec98 Reg N .0001 .838 1.79 92 1

TP 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .0001 .116 .184 72 1

DP 01634000 1BNFS010.34 Jan85-Dec98 — — — — — — 

DIP 01634000 1BNFS010.34 Jan85-Dec98 — — — — — — TSS 01634000 1BNFS010.34 Jan85-Dec98 Reg Y .0466 4.24 10.1 2 4
37 

Appendix 2. Trends in flow-weighted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR Test Log transformation p-value Base-median concentration Status-median concentration Magnitude Minimum Max

01666500 - Robinson River near Locust Dale, Va. (map ID site #23) 

TN 01666500 3-ROB001.90 Jan85-Dec98 Reg Y 0.0468 .675 .735 -27 

NOx 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0032 .560 .535 -4 -

TP 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0001 .093 .132 15 DP 01666500 3-ROB001.90 Jan85-Dec98 — — — — — — 

DIP 01666500 3-ROB001.90 Jan85-Dec98 — — — — — — TSS 01666500 3-ROB001.90 Jan85-Dec98 Reg Y .0071 5.56 28.4 55 1

01671020 - North Anna River at Hart Corner near Doswell, Va. (map ID site #26) 

TN 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .2247 .272 .341 -37 NOx 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .7326 .161 .164 -21 TP 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .0001 .110 .065 -50 -

DP 01671020 8-NAR005.42 Jan85-Dec98 — — — — — — 

DIP 01671020 8-NAR005.42 Jan85-Dec98 — — — — — — TSS 01671020 8-NAR005.42 Jan85-Dec98 Reg Y .0739 3.90 7.86 -4 1

02013100 - Jackson River below Dunlap Creek at Covington, Va. (map ID site #28)
 

TN 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .3602 .438 .448 -19 NOx 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0041 .130 .226 13 

TP 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0001 2.29 .399 -84 -

DP 02013100 2-JKS023.61 Jan85-Dec98 — — — — — — 

DIP 02013100 2-JKS023.61 Jan85-Dec98 — — — — — — TSS 02013100 2-JKS023.61 Jan85-Dec98 Reg Y .0965 7.03 8.16 -2 
APPENDIX 3—TRENDS IN FLOW-ADJUSTED CONCENTRATION
 

DATA FOR 9 RIVER INPUT MONITORING PROGRAM SITES AND
 

21 MULTI-AGENCY NONTIDAL PROGRAM SITES
 

IN THE CHESAPEAKE BAY WATERSHED
 

Parameters: TN, total nitrogen; DNH, dissolved ammonia; TNH, total ammonia; NOx, total or dissolved nitrate, or, 

nitrite plus nitrate; DKN, dissolved ammonia plus organic nitrogen; TKN, total ammonia plus organic nitrogen; 

TP, total phosphorus; DP, dissolved phosphorus; DIP, dissolved inorganic phosphorus; TSS, total suspended 

solids; SED, suspended sediment. 

Station: flow, USGS discharge site number; WQ, water-quality site number. 

Statistics: POR, time period used in test; percentage less than detect, percentage of samples reported at less than 

the detection limit; test, regression (Reg), Kendall Theil (KT); log transformed; yes (Y) or no (N); p-value, measure 

of significance of regressor at 0.05; slope, regression slope; base median, median of first 2 years of record; status 

median, median of last 3 years of record; magnitude, minimum (min) and maximum (max) percentage change in 

trend for indicated period of record; tend direction, UP, down (DN), or not significant (NS); relative rank, each 

individual status concentration (milligrams per liter) compared to all others of the same parameter; shaded areas 

are significant at 95-percent confidence level; —, not applicable or insufficient data. 

38 
39 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01491000 - Choptank River near Greensboro, Md. (map ID site #9) 

TN 01491000 01491000 Jan85-Dec98 0 KT 0.0963 — — -14 

TKN 01491000 01491000 Jan85-Dec98 0 KT .0000 — — -41 

NOx 01491000 01491000 Jan85-Dec98 .3 KT .0000 — — 17 TP 01491000 01491000 Jan85-Dec98 1.8 KT .0006 — — -13 

DP 01491000 01491000 Jan85-Dec98 3.2 KT .5628 — — -15 

DIP 01491000 01491000 Jan85-Dec98 4.4 KT .0634 — — 0 

SED 01491000 01491000 Jan85-Dec98 0 KT .0000 — — -33 

01578310 - Susquehanna River at Conowingo, Md. (map ID site #8) 

TN 01578310 01578310 Jan85-Dec98 0 KT .0000 — — -13 

TKN 01578310 01578310 Jan85-Dec98 0 KT .0000 — — -56 

NOx 01578310 01578310 Jan85-Dec98 0 KT .5513 — — -6 

TP 01578310 01578310 Jan85-Dec98 2.8 KT .0000 — — -36 

DP 01578310 01578310 Jan85-Dec98 3.5 KT .0000 — — -51 

DIP 01578310 01578310 Jan85-Dec98 16.1 KT .9190 — — -60 

SED 01578310 01578310 Jan85-Dec98 0 KT .0069 — — -8 

 01594440 - Patuxent River near Bowie, Md. (map ID site #11) 

TN 01594440 01594440 Jan85-Dec98 0 KT .0000 — — -60 

TKN 01594440 01594440 Jan85-Dec98 0 KT .0000 — — -68 NOx 01594440 01594440 Jan85-Dec98 0 KT .0000 — — -58 TP 01594440 01594440 Jan85-Dec98 .2 KT .0000 — — -78 DP 01594440 01594440 Jan85-Dec98 3.5 KT .0000 — — -74 DIP 01594440 01594440 Jan85-Dec98 4.1 KT .0000 — — -60 SED 01594440 01594440 Jan85-Dec98 0 KT .0000 — — -52 
40 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01646580 - Potomac River at Chain Bridge, Md. (map ID site #28) 

TN 01646580 PR01 Jan85-Dec98 0 KT 0.2020 — — 0 

TKN 01646580 PR01 Jan85-Dec98 0 KT .0000 — — -49 

NOx 01646580 PR01 Jan85-Dec98 .5 KT .0059 — — 23 TP 01646580 PR01 Jan85-Dec98 2.8 KT .0000 — — -60 DP 01646580 PR01 Jan85-Dec98 10.4 KT .0000 — — -68 

DIP 01646580 PR01 Jan85-Dec98 22 KT — — — — SED 01646580 PR01 Jan85-Dec98 0 KT .0000 — — -47 

 01668000 - Rappahannock River near Fredericksburg, Va. (map ID site #24) 

TN 01668000 01668000 Jan88-Dec98 0 KT .0000 — — -21 

NOx 01668000 01668000 Jan88-Dec98 7 KT .0196 — — -3 

TP 01668000 01668000 Jan88-Dec98 2 KT .0000 — — -41 

DIP 01668000 01668000 Jan88-Dec98 13 KT .8286 — — -29 

 01673000 - Pamunkey River near Hanover, Va. (map ID site #25) 

TN 01673000 01673000 Jan89-Dec98 0 KT .7790 — — -12 

TSS 01668000 01668000 Jan88-Dec98 18 KT .0043 — — -22 

NOx 01673000 01673000 Jan89-Dec98 0 KT .0000 — — 20 

TP 01673000 01673000 Jan89-Dec98 0 KT .2891 — — -23 

DIP 01673000 01673000 Jan89-Dec98 11 KT .0000 — — 69 

TSS 01673000 01673000 Jan89-Dec98 10 KT .7230 — — -37 

01674500 - Mattaponi River near Beulahville, Va. (map ID site #27) 

TN 01674500 01674500 Jan89-Dec98 0 KT .0000 — — -21 

NOx 01674500 01674500 Jan89-Dec98 2 KT .0088 — — -6 

TP 01674500 01674500 Jan89-Dec98 0 KT .0000 — — -25 DIP 01674500 01674500 Jan89-Dec98 14 KT .0092 — — 0 

TSS 01674500 01674500 Jan89-Dec98 18 KT .3314 — — -41 
41 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

02035000 - James River at Cartersville, Va. (map ID site #29) 

TN 02035000 02035000 Jan88-Dec98 0 KT 0.0084 — — -30 

NOx 02035000 02035000 Jan88-Dec98 2 KT .2672 — — -15 

TP 02035000 02035000 Jan88-Dec98 0 KT .0000 — — -69 

DIP 02035000 02035000 Jan88-Dec98 2 KT .0000 — — -83 

TSS 02035000 02035000 Jan88-Dec98 12 KT .9290 — — -26 

 02041650 - Appomattox River at Matoaca, Va. (map ID site #30) 

TN 02041650 02041650 Jan89-Dec98 0 KT .0000 — — -27 

NOx 02041650 02041650 Jan89-Dec98 3 KT .0337 — — -39 

TP 02041650 02041650 Jan89-Dec98 0 KT .0931 — — -31 

DIP 02041650 02041650 Jan89-Dec98 17 KT .7426 — — 0 

TSS 02041650 02041650 Jan89-Dec98 16 KT .5398 — — -15 

MULTI-AGENCY SITES 

01531500 - Susquehanna River at Towanda, Pa. (map ID site #1) 

TN 01531500 TOW Jan89-Dec98 0 KT .0000 1.35 1.01 -22 

NOx 01531500 TOW Jan89-Dec98 0 KT .0000 .744 .631 -21 

TP 01531500 TOW Jan89-Dec98 .4 KT .5226 .048 .056 -45 

DP 01531500 TOW Jan89-Dec98 1.1 KT .0000 .031 .024 -37 

DIP 01531500 TOW Jan89-Dec98 2.6 KT .0114 .008 .005 -76 

SED 01531500 TOW Jan89-Dec98 0 KT .4562 .8 4.2 -21 

01540500 - Susquehanna River at Danville, Pa. (map ID site #2) 

TN 01540500 DAN Jan85-Dec98 0 KT .0000 1.51 1.18 -22 

NOx 01540500 DAN Jan85-Dec98 0 KT .0526 .796 .786 -17 

TP 01540500 DAN Jan85-Dec98 .5 KT .0000 .075 .034 -30 

DP 01540500 DAN Jan85-Dec98 3.3 KT .0000 .027 .012 -54 

DIP 01540500 DAN Jan85-Dec98 20.4 — — .019 .008 — 

SED 01540500 DAN Jan85-Dec98 .5 KT .0012 36.6 23.5 -25 
42 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01553500 - West Branch Susquehanna River at Lewisburg, Pa. (map ID site #3) 

TN 01553500 LEW Jan85-Dec98 0 KT 0.0000 1.17 0.89 -16 

NOx 01553500 LEW Jan85-Dec98 0 KT .1109 .655 .581 -16 

TP 01553500 LEW Jan85-Dec98 .3 KT .0000 .034 .01 -51 

DP 01553500 LEW Jan85-Dec98 10.6 KT .0000 .02 .008 -63 

DIP 01553500 LEW Jan85-Dec98 29.9 — — .011 .007 — SED 01553500 LEW Jan85-Dec98 .9 KT .9293 11.2 12.8 -53 

01567000 - Juniata River at Newport, Pa. (map ID site #4) 

TN 01567000 JUN Jan85-Dec98 0 KT .0000 1.99 1.52 -19 

NOx 01567000 JUN Jan85-Dec98 0 KT .0000 1.53 1.2 -13 

TP 01567000 JUN Jan85-Dec98 0 KT .0000 .073 .038 -39 

DP 01567000 JUN Jan85-Dec98 1.2 KT .0000 .043 .018 -47 

DIP 01567000 JUN Jan85-Dec98 12.2 KT .0000 .017 .014 -53 

SED 01567000 JUN Jan85-Dec98 .9 KT .0015 23.3 10.6 -25 

01576000 - Susquehanna River at Marietta, Pa. (map ID site #6) 

TN 01576000 MAR Jan85-Dec98 0 KT .0000 1.62 1.34 -25 

NOx 01576000 MAR Jan85-Dec98 0 KT .0342 1.03 1.02 -1 

TP 01576000 MAR Jan85-Dec98 .3 KT .0000 .084 .043 -46 

DP 01576000 MAR Jan85-Dec98 2.4 KT .0000 .031 .016 -49 

DIP 01576000 MAR Jan85-Dec98 23.8 — — .008 .008 — 

01576754 - Conestoga River at Conestoga, Pa. (map ID site #7) 

TN 01576754 CON Jan85-Dec98 0 KT .3555 8.74 8.86 -12 

NOx 01576754 CON Jan85-Dec98 0 KT .3276 6.26 6.84 -5 

SED 01576000 MAR Jan85-Dec98 1.2 KT .0013 39.7 24.5 -24 

TP 01576754 CON Jan85-Dec98 0 KT .0000 .382 .139 -44 

DP 01576754 CON Jan85-Dec98 0 KT .0000 .247 .112 -55 

DIP 01576754 CON Jan85-Dec98 .5 KT .0000 .178 .063 -60 

SED 01576754 CON Jan85-Dec98 .9 KT .0060 56 55.9 -13 
43 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01570000 - Conodoguinet Creek near Hogestown, Pa. (map ID site #5) 

TN 01570000 WQN0213 Jan85-Dec98 12 KT 0.1915 — — -21 

NOx 01570000 WQN0213 Jan85-Dec98 — — — — — — TP 01570000 WQN0213 Jan85-Dec98 13 KT .0000 — — -69 

DP 01570000 WQN0213 Jan85-Dec98 20 KT .0000 — — -85 

DIP 01570000 WQN0213 Jan85-Dec98 — — — — — — TSS 01570000 WQN0213 Jan85-Dec98 — — — — — — 

01586000 - North Branch Patapsco River at Cedarhurst, Md. (map ID site #12) 

TN 01586000 NPA0165 Jan85-Dec98 0 KT .0000 — — 27 

NOx 01586000 NPA0165 Jan85-Dec98 0 KT .0000 — — 46 TP 01586000 NPA0165 Jan85-Dec98 7.6 KT .0000 — — -75 

DIP 01586000 NPA0165 Jan85-Dec98 — — — — — — TSS 01586000 NPA0165 Jan85-Dec98 4.8 KT .0015 — — -70 

01592500 - Patuxent River near Laurel, Md. (map ID site #10) 

TN 01592500 PXT0809 Jan85-Dec98 0 KT .0010 — — 14 

NOx 01592500 PXT0809 Jan85-Dec98 0 KT .0385 — — 14 TP 01592500 PXT0809 Jan85-Dec98 2.4 KT .8396 — — -8 

DIP 01592500 PXT0809 Jan85-Dec98 — — — — — — 

TSS 01592500 PXT0809 Jan85-Dec98 2.4 KT .0238 — — 52 

01599000 - Georges Creek near Franklin, Md. (map ID site #13) 

TN 01599000 GEO0009 Jan85-Dec98 0 KT .0000 — — -31 NOx 01599000 GEO0009 Jan85-Dec98 0 KT .0328 — — 69 TP 01599000 GEO0009 Jan85-Dec98 2.4 KT .0000 — — -73 

DIP 01599000 GEO0009 Jan85-Dec98 — — — — — — TSS 01599000 GEO0009 Jan85-Dec98 .6 KT .7241 — — -13 
44 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01601500 - Wills Creek near Cumberland, Md. (map ID site #14) 

TN 01601500 WIL0013 Jan85-Dec98 0 KT 0.0000 — — -43 

NOx 01601500 WIL0013 Jan85-Dec98 0 KT .8709 — — 8 

TP 01601500 WIL0013 Jan85-Dec98 17 KT .6495 — — -29 

DIP 01601500 WIL0013 Jan85-Dec98 — — — — — — TSS 01601500 WIL0013 Jan85-Dec98 8.5 KT .5798 — — -10 

01610000 - Potomac River at Paw Paw, W. Va. (map ID site #15) 

TN 01610000 POT2766 Jan85-Dec98 0 KT .0007 — — -19 

NOx 01610000 POT2766 Jan85-Dec98 0 KT .0010 — — 277 TP 01610000 POT2766 Jan85-Dec98 3.9 KT .0004 — — -50 

DIP 01610000 POT2766 Jan85-Dec98 — — — — — — TSS 01610000 POT2766 Jan85-Dec98 6 KT .0233 — — -43 

01613000 - Potomac River at Hancock, Md. (map ID site #16) 

TN 01613000 POT2386 Jan85-Dec98 0 KT .0000 — — -33 

NOx 01613000 POT2386 Jan85-Dec98 0 KT .9278 — — -12 

TP 01613000 POT2386 Jan85-Dec98 3.8 KT .0000 — — -53 

DIP 01613000 POT2386 Jan85-Dec98 — — — — — — TSS 01613000 POT2386 Jan85-Dec98 6.7 KT .0639 — — -43 

01614500 - Conococheague Creek at Fairview, Md. (map ID site #17) 

TN 01614500 CON0180 Jan85-Dec98 0 KT .0003 — — -15 

NOx 01614500 CON0180 Jan85-Dec98 0 KT .0611 — — 10 TP 01614500 CON0180 Jan85-Dec98 .6 KT .0000 — — -53 

DIP 01614500 CON0180 Jan85-Dec98 — — — — — — TSS 01614500 CON0180 Jan85-Dec98 5.5 KT .0015 — — -42 
45 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01638500 - Potomac River at Point of Rocks, Md. (map ID site #19) 

TN 01638500 POT1595 Jan85-Dec98 0 KT 0.0009 — — -17 

NOx 01638500 POT1595 Jan85-Dec98 0 — .0158 — — 20 TP 01638500 POT1595 Jan85-Dec98 .6 KT .0000 — — -57 

DIP 01638500 POT1595 Jan85-Dec98 — — — — — — TSS 01638500 POT1595 Jan85-Dec98 3.6 KT .0069 — — -37 

01643000 - Monocacy River at Reels Mill Road, Md. (map ID site #18) 

TN 01643000 MON0528 Jan85-Dec98 0 KT .0000 — — -49 

NOx 01643000 MON0528 Jan85-Dec98 0 KT .5638 — — -7 

TP 01643000 MON0528 Jan85-Dec98 0 KT .0000 — — -56 

DIP 01643000 MON0528 Jan85-Dec98 — — — — — — TSS 01643000 MON0528 Jan85-Dec98 0 KT .3766 — — -16 

01631000 - S. Fork Shenandoah River near Front Royal, Va. (map ID site #20) 

TN 01631000 1BSSF003.56 Jan85-Dec98 36 — — — — — NOx 01631000 1BSSF003.56 Jan85-Dec98 .8 KT .3420 — — 2 

TP 01631000 1BSSF003.56 Jan85-Dec98 20 KT .0676 — — — DP 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — DIP 01631000 1BSSF003.56 Jan85-Dec98 — — — — — — TSS 01631000 1BSSF003.56 Jan85-Dec98 41 — — — — — 

01634000 - N. Fork Shenandoah River near Strasburg, Va. (map ID site #21)
 

TN 01634000 1BNFS010.34 Jan85-Dec98 20 KT .3035 — — 7 NOx 01634000 1BNFS010.34 Jan85-Dec98 3.2 KT .0514 — — 23 TP 01634000 1BNFS010.34 Jan85-Dec98 31 — — — — — 

DP 01634000 1BNFS010.34 Jan85-Dec98 — — — — — — DIP 01634000 1BNFS010.34 Jan85-Dec98 — — — — — — TSS 01634000 1BNFS010.34 Jan85-Dec98 53 — — — — — 
46 

Appendix 3. Trends in flow-adjusted concentration data for 9 River Input Monitoring Program sites and 21 Multi-Agency Nontidal Progra

Bay Watershed—Continued 

Station Statistics 

Parameter 

Flow WQ POR 

Percentage 

less than 

detect 

Test p-value 0.05 Base-median concentration Status-median concentration M

Minimu

01666500 - Robinson River near Locust Dale, Va. (map ID site #23) 

TN 01666500 3-ROB001.90 Jan85-Dec98 43 — — — — — 

NOx 01666500 3-ROB001.90 Jan85-Dec98 0 KT 0.0060 — — -17 

TP 01666500 3-ROB001.90 Jan85-Dec98 56 — — — — — DP 01666500 3-ROB001.90 Jan85-Dec98 — — — — — — DIP 01666500 3-ROB001.90 Jan85-Dec98 — — — — — — TSS 01666500 3-ROB001.90 Jan85-Dec98 23 — — — — — 

01671020 - North Anna River at Hart Corner near Doswell, Va. (map ID site #26) 

TN 01671020 8-NAR005.42 Jan85-Dec98 62 — — — — — 

NOx 01671020 8-NAR005.42 Jan85-Dec98 20 KT .6587 — — -7 TP 01671020 8-NAR005.42 Jan85-Dec98 35 — — — — — DP 01671020 8-NAR005.42 Jan85-Dec98 — — — — — — DIP 01671020 8-NAR005.42 Jan85-Dec98 — — — — — — TSS 01671020 8-NAR005.42 Jan85-Dec98 57 — — — — — 

02013100 - Jackson River below Dunlap Creek at Covington, Va. (map ID site #28) 

TN 02013100 2-JKS023.61 Jan85-Dec98 46 — — — — — 

NOx 02013100 2-JKS023.61 Jan85-Dec98 5.7 KT .4423 — — 4 

TP 02013100 2-JKS023.61 Jan85-Dec98 2.1 KT .0000 — — -119 

DP 02013100 2-JKS023.61 Jan85-Dec98 — — — — — — DIP 02013100 2-JKS023.61 Jan85-Dec98 — — — — — — TSS 02013100 2-JKS023.61 Jan85-Dec98 9.9 KT .1102 — — -28